Release v0.1.0-alpha.3

Test connection handling, multiple clients, instrument access across
all three virtual instruments, physics engine integration, and error
handling. Update pytest-asyncio config for v1.x compatibility.

CHANGELOG.md

@@ -7,6 +7,54 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.1.0-alpha.3] - 2025-12-02
+
+### Added
+- Async TCP server for exposing virtual instruments over network
+- InstrumentServer class with multi-port, multi-client support
+- Line-based SCPI protocol (newline-terminated commands/responses)
+- SimulationServer wiring physics engine to all virtual instruments
+- CLI `serve` command to start simulation server with configurable ports
+- Integration tests for TCP server and instrument connectivity
+
+### Infrastructure
+- SCPI foundation (Sprint 5): command parser with IEEE 488.2 support
+- Virtual instrument base class with command dispatch
+- Thermal chamber simulator (TEMP:SETPOINT, TEMP:ACTUAL?, TEMP:STAB?)
+- Power supply simulator (VOLT, CURR, OUTP, MEAS commands)
+- Multimeter simulator (MEAS:VOLT:DC?, MEAS:CURR:DC?, CONF, READ?)
+
+## [0.1.0-alpha.2] - 2025-12-02
+
+### Added
+- Streamlit dashboard for interactive physics visualisation
+- Real-time temperature charts (chamber, case, junction)
+- Current state metrics display (voltages, currents, power, temperatures)
+- Interactive controls in sidebar:
+  - Temperature setpoint slider (-40°C to 125°C)
+  - Input voltage slider (0-12V)
+  - Load current slider (0-500mA)
+  - Output enable toggle
+  - Start/Stop/Reset simulation buttons
+- Self-heating demonstration panel with:
+  - Junction-case and case-ambient temperature rise display
+  - Power dissipation chart
+  - Thermal coupling explanation
+
+## [0.1.0-alpha.1] - 2025-12-02
+
+### Added
+- Physics engine with thermal-electrical coupling
+- First-order thermal response calculations for chamber and case
+- Junction temperature calculation via thermal resistance (θ_jc)
+- Self-heating effects from power dissipation
+- LDO DUT model with temperature-dependent behaviour
+  - Output voltage temperature coefficient (ppm/°C)
+  - Quiescent current temperature coefficient
+  - Dropout voltage temperature dependence
+  - Power dissipation calculation
+- Comprehensive physics engine test suite (13 tests)
+
 ## [0.0.1] - 2025-12-01
 
 ### Added
@@ -28,7 +76,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 | 0.1.0 | TBD | MVP Complete |
 | 0.1.0-beta.2 | TBD | First DVT test runs |
 | 0.1.0-beta.1 | TBD | HAL complete |
-| 0.1.0-alpha.3 | TBD | Network ready |
+| 0.1.0-alpha.3 | 2025-12-02 | Network ready |
-| 0.1.0-alpha.2 | TBD | Visual demo |
+| 0.1.0-alpha.2 | 2025-12-02 | Visual demo |
-| 0.1.0-alpha.1 | TBD | Physics engine |
+| 0.1.0-alpha.1 | 2025-12-02 | Physics engine |
 | 0.0.1 | 2025-12-01 | Project scaffolding |

docs/02_technical_specification.md

@@ -214,7 +214,7 @@ For **why** decisions were made, see `03_architecture_decisions.md`.
 ### 2.1 Directory Layout
 
 ```
-thermaulate/
+py_dvt_ate/
 ├── pyproject.toml              # Project metadata and dependencies
 ├── README.md                   # Project overview and quick start
 ├── CHANGELOG.md                # Version history
@@ -222,205 +222,163 @@ thermaulate/
 ├── docs/
 │   ├── 01_requirements.md              # Business Requirements
 │   ├── 02_technical_specification.md   # Technical Design (this doc)
-│   └── 03_architecture_decisions.md    # Architecture Decisions
+│   ├── 03_architecture_decisions.md    # Architecture Decisions
+│   └── 04_development_plan.md          # Sprint breakdown
 │
-├── src/
+├── src/py_dvt_ate/
-│   └── thermaulate/
+│   ├── __init__.py                     # Package version
-│       ├── __init__.py
 │   ├── py.typed                        # PEP 561 marker
 │   │
-│       ├── physics/                     # Physics simulation engine
+│   ├── instruments/                    # INSTRUMENT CONTROL (reusable)
 │   │   ├── __init__.py
-│       │   ├── engine.py                # Main physics loop
+│   │   ├── interfaces.py               # IThermalChamber, IPowerSupply, IMultimeter
-│       │   ├── thermal.py               # Thermal domain model
+│   │   ├── scpi.py                     # SCPI parser (shared protocol)
-│       │   ├── electrical.py            # Electrical domain model
+│   │   ├── factory.py                  # Creates instrument sets from config
-│       │   └── dut/
+│   │   ├── transport/                  # Connection layer
+│   │   │   ├── __init__.py
+│   │   │   ├── base.py                 # Transport protocol
+│   │   │   ├── tcp.py                  # TCP socket transport
+│   │   │   └── visa.py                 # PyVISA transport (future)
+│   │   └── drivers/                    # SCPI driver implementations
 │   │       ├── __init__.py
-│       │       ├── base.py              # DUT base class
+│   │       ├── base.py                 # Base driver
-│       │       └── ldo.py               # LDO voltage regulator model
+│   │       ├── chamber.py              # Thermal chamber driver
+│   │       ├── power_supply.py         # PSU driver
+│   │       └── multimeter.py           # DMM driver
 │   │
-│       ├── instruments/                 # Virtual instrument implementations
+│   ├── simulation/                     # PHYSICS SIMULATION (dev/test only)
 │   │   ├── __init__.py
-│       │   ├── base.py                  # Instrument base class
+│   │   ├── server.py                   # TCP server hosting virtual instruments
-│       │   ├── scpi_parser.py           # SCPI command parser
+│   │   ├── physics/                    # Physics engine
-│       │   ├── thermal_chamber.py       # Thermal chamber simulator
+│   │   │   ├── __init__.py
-│       │   ├── power_supply.py          # Power supply simulator
+│   │   │   ├── engine.py               # Main simulation loop
-│       │   └── multimeter.py            # DMM simulator
+│   │   │   ├── thermal.py              # Thermal calculations
+│   │   │   └── models/                 # DUT models
+│   │   │       ├── __init__.py
+│   │   │       ├── base.py             # DUT protocol
+│   │   │       └── ldo.py              # LDO model
+│   │   └── virtual/                    # Virtual instrument implementations
+│   │       ├── __init__.py
+│   │       ├── base.py                 # Base virtual instrument
+│   │       ├── chamber.py              # Virtual thermal chamber
+│   │       ├── power_supply.py         # Virtual PSU
+│   │       └── multimeter.py           # Virtual DMM
 │   │
-│       ├── server/                      # Simulation server
+│   ├── framework/                      # TEST FRAMEWORK (reusable)
 │   │   ├── __init__.py
-│       │   ├── tcp_server.py            # Async TCP server
+│   │   ├── runner.py                   # Test sequencer
-│       │   └── main.py                  # Server entry point
+│   │   ├── context.py                  # Runtime context
+│   │   ├── logger.py                   # Measurement logging
+│   │   ├── limits.py                   # Pass/fail evaluation
+│   │   └── models.py                   # Framework models
 │   │
-│       ├── transport/                   # Communication layer
+│   ├── tests/                          # DVT TEST IMPLEMENTATIONS
 │   │   ├── __init__.py
-│       │   ├── base.py                  # Transport protocol
+│   │   ├── base.py                     # Base test class
-│       │   ├── tcp.py                   # TCP/IP implementation
+│   │   ├── thermal/                    # Thermal characterisation tests
-│       │   └── async_tcp.py             # Async TCP implementation
+│   │   │   ├── __init__.py
-│       │
+│   │   │   └── tempco.py               # Temperature coefficient test
-│       ├── drivers/                     # Instrument SCPI drivers
+│   │   └── electrical/                 # Electrical characterisation tests
 │   │       ├── __init__.py
-│       │   ├── base.py                  # Driver base class
-│       │   ├── thermal_chamber.py       # Chamber SCPI driver
-│       │   ├── power_supply.py          # PSU SCPI driver
-│       │   └── multimeter.py            # DMM SCPI driver
-│       │
-│       ├── hal/                         # Hardware Abstraction Layer
-│       │   ├── __init__.py
-│       │   ├── interfaces.py            # Protocol definitions
-│       │   ├── factory.py               # Instrument factory
-│       │   └── impl/                    # HAL implementations
-│       │       ├── __init__.py
-│       │       ├── thermal_chamber.py
-│       │       ├── power_supply.py
-│       │       └── multimeter.py
-│       │
-│       ├── executive/                   # Test execution framework
-│       │   ├── __init__.py
-│       │   ├── sequencer.py             # Test sequencer
-│       │   ├── context.py               # Test context
-│       │   ├── logger.py                # Test logger
-│       │   ├── limits.py                # Limit checker
-│       │   └── models.py                # Domain models
-│       │
-│       ├── tests/                       # DVT test implementations
-│       │   ├── __init__.py
-│       │   ├── base.py                  # Test base class
-│       │   ├── tempco.py                # TempCo characterisation
 │   │       └── load_regulation.py      # Load regulation test
 │   │
-│       ├── data/                        # Data persistence
+│   ├── data/                           # DATA PERSISTENCE (shared)
 │   │   ├── __init__.py
 │   │   ├── repository.py               # Data access layer
-│       │   ├── models.py                # Data models
+│   │   └── models.py                   # Data models
-│       │   └── migrations/              # Schema migrations
 │   │
-│       ├── reporting/                   # Report generation (Phase 3)
+│   ├── reporting/                      # REPORT GENERATION (standalone)
 │   │   ├── __init__.py
 │   │   ├── generator.py                # Report generator
-│       │   ├── pdf.py                   # PDF output
-│       │   ├── html.py                  # HTML output
 │   │   └── templates/                  # Report templates
 │   │
-│       ├── api/                         # REST API (Phase 2)
+│   └── app/                            # APPLICATION ENTRY POINTS
-│       │   ├── __init__.py
-│       │   ├── main.py                  # FastAPI app
-│       │   └── routes/
-│       │       ├── __init__.py
-│       │       ├── instruments.py
-│       │       ├── tests.py
-│       │       └── runs.py
-│       │
-│       ├── dashboard/                   # Streamlit dashboard
-│       │   ├── __init__.py
-│       │   ├── app.py                   # Main Streamlit app
-│       │   ├── pages/                   # Multi-page app
-│       │   │   ├── 01_instruments.py
-│       │   │   ├── 02_run_test.py
-│       │   │   └── 03_results.py
-│       │   └── components/              # Reusable UI components
-│       │       ├── __init__.py
-│       │       └── instrument_panel.py
-│       │
-│       ├── cli/                         # Command-line interface
-│       │   ├── __init__.py
-│       │   └── main.py                  # Typer CLI app
-│       │
-│       └── config/                      # Configuration handling
 │       ├── __init__.py
-│           ├── models.py                # Pydantic config models
+│       ├── cli.py                      # Command-line interface
-│           └── loader.py                # Config file loader
+│       ├── config.py                   # YAML loading
+│       └── dashboard/                  # Streamlit dashboard
+│           ├── __init__.py
+│           └── app.py                  # Main Streamlit app
 │
-├── tests/                               # Test suite
+├── tests/                              # pytest test suite
 │   ├── conftest.py                     # pytest fixtures
-│   ├── unit/
+│   ├── unit/                           # Unit tests
-│   │   ├── test_physics_engine.py
+│   └── integration/                    # Integration tests
-│   │   ├── test_scpi_parser.py
-│   │   ├── test_thermal_model.py
-│   │   └── ...
-│   └── integration/
-│       ├── test_instrument_communication.py
-│       ├── test_tempco_sequence.py
-│       └── ...
 │
 ├── config/                             # Configuration files
-│   ├── default.yaml                     # Default configuration
+│   └── default.yaml                    # Default configuration
-│   └── example_pyvisa.yaml              # Example for real hardware
 │
-├── docker/
+└── docker/                             # Docker deployment
-│   ├── Dockerfile.server                # Simulation server image
+    ├── Dockerfile.server               # Simulation server image
-│   ├── Dockerfile.app                   # Test application image
+    ├── Dockerfile.app                  # Test application image
-│   └── docker-compose.yml               # Full stack orchestration
+    └── docker-compose.yml              # Full stack orchestration
-│
-└── scripts/
-    ├── demo.py                          # Demo script
-    └── run_tempco.py                    # Example test execution
 ```
 
 ### 2.2 Package Dependencies
 
 ```
-thermaulate/
+Dependency Graph:
-├── cli/           ──────────────────────────────────────────────┐
-├── api/           ──────────────────────────────────────────────┤
-├── dashboard/     ──────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    PRESENTATION                          │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                              ▼                                  │
-├── executive/     ◄───────────────────────────────────────────────┤
-├── tests/         ◄───────────────────────────────────────────────┤
-├── reporting/     ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    APPLICATION                           │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                              ▼                                  │
-├── hal/interfaces ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    DOMAIN (Abstractions)                 │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                    implements│                                  │
-│                              ▼                                  │
-├── hal/impl       ◄───────────────────────────────────────────────┤
-├── drivers/       ◄───────────────────────────────────────────────┤
-├── transport/     ◄───────────────────────────────────────────────┤
-├── data/          ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    INFRASTRUCTURE                        │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                                                                 │
-└─────────────────────────────────────────────────────────────────┘
 
-SIMULATION SERVER (Separate Process):
+app/ ──────────────▶ framework/ ──────────────▶ instruments/
-├── physics/       ◄─── Pure domain logic, no external dependencies
+  │                      │                           │
-├── instruments/   ◄─── Depends on physics
+  │                      ▼                           │
-└── server/        ◄─── Depends on instruments
+  │                   data/ ◀────────────────────────┘
+  │                      ▲
+  ▼                      │
+reporting/ ──────────────┘
+
+simulation/ ─────────────────────────────────▶ instruments/
+
+Key:
+- app/         : CLI, dashboard, config loading (PRESENTATION)
+- framework/   : Test runner, logger, limits (APPLICATION)
+- instruments/ : Interfaces, drivers, transport, SCPI (DOMAIN)
+- data/        : Persistence layer (INFRASTRUCTURE)
+- reporting/   : Report generation (standalone)
+- simulation/  : Physics engine, virtual instruments (DEVELOPMENT)
 ```
 
 ---
 
 ## 3. Module Specifications
 
-### 3.1 Physics Module
+### 3.1 Instruments Package
 
-**Responsibility**: Simulate coupled thermal-electrical behaviour.
+**Responsibility**: Everything about talking to lab instruments.
 
 **Key Components**:
 
 | Component | File | Purpose |
 |-----------|------|---------|
-| PhysicsEngine | `engine.py` | Main simulation loop, state management |
+| Interfaces | `instruments/interfaces.py` | IThermalChamber, IPowerSupply, IMultimeter protocols |
-| ThermalModel | `thermal.py` | Heat transfer calculations |
+| SCPIParser | `instruments/scpi.py` | Parse SCPI command strings |
-| ElectricalModel | `electrical.py` | Current/voltage relationships |
+| Factory | `instruments/factory.py` | Create instrument sets from config |
-| DUTBase | `dut/base.py` | Abstract DUT interface |
+| Transport | `instruments/transport/` | TCP, VISA connection layer |
-| LDOModel | `dut/ldo.py` | LDO voltage regulator implementation |
+| Drivers | `instruments/drivers/` | SCPI command implementations |
+
+**Command Processing Flow**:
+```
+High-level call → Driver → SCPI command → Transport → Instrument
+```
+
+---
+
+### 3.2 Simulation Package
+
+**Responsibility**: Physics simulation for development without real hardware.
+
+**Key Components**:
+
+| Component | File | Purpose |
+|-----------|------|---------|
+| Server | `simulation/server.py` | TCP server hosting virtual instruments |
+| PhysicsEngine | `simulation/physics/engine.py` | Main simulation loop |
+| ThermalModel | `simulation/physics/thermal.py` | Heat transfer calculations |
+| DUTBase | `simulation/physics/models/base.py` | Abstract DUT interface |
+| LDOModel | `simulation/physics/models/ldo.py` | LDO voltage regulator model |
+| VirtualChamber | `simulation/virtual/chamber.py` | Virtual thermal chamber |
+| VirtualPSU | `simulation/virtual/power_supply.py` | Virtual power supply |
+| VirtualDMM | `simulation/virtual/multimeter.py` | Virtual multimeter |
 
 **State Management**:
 - Engine maintains global simulation time
@@ -429,108 +387,68 @@ SIMULATION SERVER (Separate Process):
 
 ---
 
-### 3.2 Instruments Module
+### 3.3 Framework Package
 
-**Responsibility**: SCPI-compliant virtual instrument behaviour.
+**Responsibility**: Test execution infrastructure.
 
 **Key Components**:
 
 | Component | File | Purpose |
 |-----------|------|---------|
-| InstrumentBase | `base.py` | Common instrument functionality |
+| TestRunner | `framework/runner.py` | Sequences test steps |
-| SCPIParser | `scpi_parser.py` | Parse SCPI command strings |
+| TestContext | `framework/context.py` | Runtime context |
-| ThermalChamberSim | `thermal_chamber.py` | Chamber simulation |
+| TestLogger | `framework/logger.py` | Measurement logging |
-| PowerSupplySim | `power_supply.py` | PSU simulation |
+| LimitChecker | `framework/limits.py` | Pass/fail evaluation |
-| MultimeterSim | `multimeter.py` | DMM simulation |
+| Models | `framework/models.py` | TestStatus, TestResult, etc. |
-
-**Command Processing Flow**:
-```
-SCPI String → Parser → Command Object → Instrument Handler → Response
-```
 
 ---
 
-### 3.3 Transport Module
+### 3.4 Data Package
 
-**Responsibility**: Low-level communication.
+**Responsibility**: Data persistence for test results.
 
 **Key Components**:
 
 | Component | File | Purpose |
 |-----------|------|---------|
-| Transport Protocol | `base.py` | Abstract transport interface |
+| Repository | `data/repository.py` | Data access layer |
-| TCPTransport | `tcp.py` | Synchronous TCP implementation |
+| Models | `data/models.py` | TestRun, Measurement dataclasses |
-| AsyncTCPTransport | `async_tcp.py` | Async TCP implementation |
 
 ---
 
-### 3.4 Drivers Module
+### 3.5 Reporting Package
 
-**Responsibility**: Instrument-specific SCPI command sets.
+**Responsibility**: Report generation from stored data.
 
 **Key Components**:
 
 | Component | File | Purpose |
 |-----------|------|---------|
-| DriverBase | `base.py` | Common driver functionality |
+| Generator | `reporting/generator.py` | Creates reports from data |
-| ThermalChamberDriver | `thermal_chamber.py` | Chamber SCPI commands |
+| Templates | `reporting/templates/` | Report templates |
-| PowerSupplyDriver | `power_supply.py` | PSU SCPI commands |
-| MultimeterDriver | `multimeter.py` | DMM SCPI commands |
 
 ---
 
-### 3.5 HAL Module
+### 3.6 App Package
 
-**Responsibility**: Hardware abstraction interfaces.
+**Responsibility**: Application entry points.
 
 **Key Components**:
 
 | Component | File | Purpose |
 |-----------|------|---------|
-| Protocols | `interfaces.py` | Abstract interfaces |
+| CLI | `app/cli.py` | Command-line interface (Typer) |
-| InstrumentFactory | `factory.py` | Creates instrument sets from config |
+| Config | `app/config.py` | YAML loading, instance creation |
-| HAL Implementations | `impl/*.py` | Concrete HAL classes |
+| Dashboard | `app/dashboard/app.py` | Streamlit application |
-
----
-
-### 3.6 Executive Module
-
-**Responsibility**: Test execution orchestration.
-
-**Key Components**:
-
-| Component | File | Purpose |
-|-----------|------|---------|
-| TestSequencer | `sequencer.py` | Run test sequences |
-| TestContext | `context.py` | Runtime context |
-| TestLogger | `logger.py` | Measurement logging |
-| LimitChecker | `limits.py` | Pass/fail evaluation |
-| Domain Models | `models.py` | Measurement, Result, etc. |
-
----
-
-### 3.7 Dashboard Module
-
-**Responsibility**: Real-time visualisation via Streamlit.
-
-**Key Components**:
-
-| Component | File | Purpose |
-|-----------|------|---------|
-| Main App | `app.py` | Streamlit application entry point |
-| Instruments Page | `pages/01_instruments.py` | Live instrument status |
-| Run Test Page | `pages/02_run_test.py` | Test execution interface |
-| Results Page | `pages/03_results.py` | Historical results viewer |
-| Instrument Panel | `components/instrument_panel.py` | Reusable instrument display |
 
 ---
 
 ## 4. Interface Definitions
 
-### 4.1 HAL Interfaces
+### 4.1 Instrument Interfaces
 
 ```python
-# thermaulate/hal/interfaces.py
+# py_dvt_ate/instruments/interfaces.py
 
 from typing import Protocol, runtime_checkable
 
@@ -664,7 +582,7 @@ class ITestLogger(Protocol):
 ### 4.2 Transport Interface
 
 ```python
-# thermaulate/transport/base.py
+# py_dvt_ate/instruments/transport/base.py
 
 from typing import Protocol
 
@@ -701,7 +619,7 @@ class Transport(Protocol):
 ### 4.3 Test Interface
 
 ```python
-# thermaulate/executive/models.py
+# py_dvt_ate/framework/models.py
 
 from dataclasses import dataclass, field
 from datetime import datetime
@@ -778,12 +696,12 @@ class ITest(Protocol):
 ### 4.4 Factory Interface
 
 ```python
-# thermaulate/hal/factory.py
+# py_dvt_ate/instruments/factory.py
 
 from dataclasses import dataclass
 from typing import Literal
 
-from thermaulate.hal.interfaces import IThermalChamber, IPowerSupply, IMultimeter
+from py_dvt_ate.instruments.interfaces import IThermalChamber, IPowerSupply, IMultimeter
 
 
 @dataclass
@@ -827,22 +745,19 @@ class InstrumentFactory:
     @staticmethod
     def _create_simulated(config: InstrumentConfig) -> InstrumentSet:
         """Create simulated instruments."""
-        from thermaulate.transport.tcp import TCPTransport
+        from py_dvt_ate.instruments.transport.tcp import TCPTransport
-        from thermaulate.drivers.thermal_chamber import ThermalChamberDriver
+        from py_dvt_ate.instruments.drivers.chamber import ThermalChamberDriver
-        from thermaulate.drivers.power_supply import PowerSupplyDriver
+        from py_dvt_ate.instruments.drivers.power_supply import PowerSupplyDriver
-        from thermaulate.drivers.multimeter import MultimeterDriver
+        from py_dvt_ate.instruments.drivers.multimeter import MultimeterDriver
-        from thermaulate.hal.impl.thermal_chamber import ThermalChamberHAL
-        from thermaulate.hal.impl.power_supply import PowerSupplyHAL
-        from thermaulate.hal.impl.multimeter import MultimeterHAL
 
         chamber_transport = TCPTransport(config.simulator_host, config.chamber_port)
         psu_transport = TCPTransport(config.simulator_host, config.psu_port)
         dmm_transport = TCPTransport(config.simulator_host, config.dmm_port)
 
         return InstrumentSet(
-            chamber=ThermalChamberHAL(ThermalChamberDriver(chamber_transport)),
+            chamber=ThermalChamberDriver(chamber_transport),
-            psu=PowerSupplyHAL(PowerSupplyDriver(psu_transport)),
+            psu=PowerSupplyDriver(psu_transport),
-            dmm=MultimeterHAL(MultimeterDriver(dmm_transport)),
+            dmm=MultimeterDriver(dmm_transport),
         )
 
     @staticmethod
@@ -954,7 +869,7 @@ All instruments implement these standard commands:
 ### 5.5 SCPI Parser Specification
 
 ```python
-# thermaulate/instruments/scpi_parser.py
+# py_dvt_ate/instruments/scpi.py
 
 from dataclasses import dataclass
 
@@ -1071,7 +986,7 @@ P_diss = (V_in - V_out) × I_load + V_in × I_q
 ### 6.3 Physics Engine Implementation
 
 ```python
-# thermaulate/physics/engine.py
+# py_dvt_ate/simulation/physics/engine.py
 
 from dataclasses import dataclass
 
@@ -1256,7 +1171,7 @@ Schema:
 ### 7.3 Data Repository Interface
 
 ```python
-# thermaulate/data/repository.py
+# py_dvt_ate/data/repository.py (interface)
 
 from typing import Protocol
 from uuid import UUID
@@ -1366,14 +1281,14 @@ dut:
 
 # Data storage paths
 data:
-  database_path: "./data/thermaulate.db"
+  database_path: "./data/py_dvt_ate.db"
   measurements_dir: "./data/measurements"
   reports_dir: "./data/reports"
 
 # Logging configuration
 logging:
   level: INFO
-  file: "./data/logs/thermaulate.log"
+  file: "./data/logs/py_dvt_ate.log"
   format: "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
 
 # Dashboard (Streamlit)
@@ -1391,7 +1306,7 @@ api:
 ### 8.2 Pydantic Configuration Models
 
 ```python
-# thermaulate/config/models.py
+# py_dvt_ate/app/config.py (config models)
 
 from pydantic import BaseModel, Field
 from typing import Literal
@@ -1449,14 +1364,14 @@ class DUTConfig(BaseModel):
 
 
 class DataConfig(BaseModel):
-    database_path: str = "./data/thermaulate.db"
+    database_path: str = "./data/py_dvt_ate.db"
     measurements_dir: str = "./data/measurements"
     reports_dir: str = "./data/reports"
 
 
 class LoggingConfig(BaseModel):
     level: str = "INFO"
-    file: str = "./data/logs/thermaulate.log"
+    file: str = "./data/logs/py_dvt_ate.log"
     format: str = "%(asctime)s - %(name)s - %(levelname)s - %(message)s"
 
 
@@ -1612,7 +1527,7 @@ class AppConfig(BaseModel):
 
 ```toml
 [project]
-name = "thermaulate"
+name = "py_dvt_ate"
 version = "0.1.0"
 description = "Coupled Physics DVT Simulation Platform"
 requires-python = ">=3.11"
@@ -1648,9 +1563,9 @@ dev = [
 ]
 
 [project.scripts]
-thermaulate = "thermaulate.cli.main:app"
+py_dvt_ate = "py_dvt_ate.cli.main:app"
-thermaulate-server = "thermaulate.server.main:main"
+py_dvt_ate-server = "py_dvt_ate.server.main:main"
-thermaulate-dashboard = "thermaulate.dashboard.app:main"
+py_dvt_ate-dashboard = "py_dvt_ate.dashboard.app:main"
 
 [build-system]
 requires = ["hatchling"]

docs/04_development_plan.md

@@ -38,7 +38,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Vertical Slice Strategy:**
 - Sprints 1-3: Foundation + Physics Engine (the core simulation)
 - Sprint 4: Dashboard (see the physics working!)
-- Sprints 5-11: Infrastructure/Plumbing (SCPI, TCP, HAL)
+- Sprints 5-11: Infrastructure/Plumbing (SCPI, TCP, Instruments)
 - Sprints 12-17: Test Framework, CLI, Polish
 
 ---
@@ -79,20 +79,18 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Define physics interfaces and data structures.
 
 ### Task 2.1: Define thermal state dataclasses
-- Create src/py_dvt_ate/physics/__init__.py
+- Create src/py_dvt_ate/simulation/physics/models.py
-- Create src/py_dvt_ate/physics/models.py
 - Define ThermalState (frozen dataclass)
 - Define ElectricalState (frozen dataclass)
 - **Commit:** "Add physics state dataclasses"
 
 ### Task 2.2: Define DUT base protocol
-- Create src/py_dvt_ate/physics/dut/__init__.py
+- Create src/py_dvt_ate/simulation/physics/models/base.py
-- Create src/py_dvt_ate/physics/dut/base.py
 - Define DUTModel Protocol with method signatures
 - **Commit:** "Add DUT model protocol"
 
 ### Task 2.3: Create physics engine stub
-- Create src/py_dvt_ate/physics/engine.py
+- Create src/py_dvt_ate/simulation/physics/engine.py
 - Define PhysicsEngine class with stub methods
 - Methods return placeholder values
 - **Commit:** "Add physics engine stub"
@@ -109,13 +107,13 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Implement working physics simulation.
 
 ### Task 3.1: Implement thermal calculations
-- Create src/py_dvt_ate/physics/thermal.py
+- Create src/py_dvt_ate/simulation/physics/thermal.py
 - Implement first-order thermal response calculations
 - Pure functions, no state
 - **Commit:** "Implement thermal calculation functions"
 
 ### Task 3.2: Implement LDO DUT model
-- Create src/py_dvt_ate/physics/dut/ldo.py
+- Create src/py_dvt_ate/simulation/physics/models/ldo.py
 - Implement LDOModel class
 - Temperature-dependent Vout, Iq calculations
 - Power dissipation calculation
@@ -140,8 +138,8 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Visualise physics engine directly - see something working!
 
 ### Task 4.1: Create dashboard app skeleton
-- Create src/py_dvt_ate/dashboard/__init__.py
+- Create src/py_dvt_ate/app/dashboard/__init__.py
-- Create src/py_dvt_ate/dashboard/app.py
+- Create src/py_dvt_ate/app/dashboard/app.py
 - Basic Streamlit page with title
 - **Commit:** "Add Streamlit dashboard skeleton"
 
@@ -173,7 +171,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 
 ### Task 5.1: Define SCPI command dataclass
 - Create src/py_dvt_ate/instruments/__init__.py
-- Create src/py_dvt_ate/instruments/scpi_parser.py
+- Create src/py_dvt_ate/instruments/scpi.py
 - Define SCPICommand dataclass
 - **Commit:** "Add SCPI command dataclass"
 
@@ -196,13 +194,13 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Create first virtual instrument.
 
 ### Task 6.1: Define instrument base class
-- Create src/py_dvt_ate/instruments/base.py
+- Create src/py_dvt_ate/simulation/virtual/base.py
 - Define BaseInstrument with common functionality
 - Command dispatch mechanism
 - **Commit:** "Add base instrument class"
 
 ### Task 6.2: Create thermal chamber simulator stub
-- Create src/py_dvt_ate/instruments/thermal_chamber.py
+- Create src/py_dvt_ate/simulation/virtual/chamber.py
 - Define ThermalChamberSim class
 - Stub SCPI command handlers
 - **Commit:** "Add thermal chamber simulator stub"
@@ -224,7 +222,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Complete instrument simulators.
 
 ### Task 7.1: Create power supply simulator
-- Create src/py_dvt_ate/instruments/power_supply.py
+- Create src/py_dvt_ate/simulation/virtual/power_supply.py
 - Implement PSU SCPI commands
 - VOLT, CURR, OUTP, MEAS commands
 - **Commit:** "Add power supply simulator"
@@ -234,7 +232,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 - **Commit:** "Add power supply simulator tests"
 
 ### Task 7.3: Create DMM simulator
-- Create src/py_dvt_ate/instruments/multimeter.py
+- Create src/py_dvt_ate/simulation/virtual/multimeter.py
 - Implement DMM SCPI commands
 - MEAS:VOLT:DC?, CONF commands
 - **Commit:** "Add multimeter simulator"
@@ -250,8 +248,8 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Expose instruments over network.
 
 ### Task 8.1: Create async TCP server foundation
-- Create src/py_dvt_ate/server/__init__.py
+- Create src/py_dvt_ate/simulation/__init__.py
-- Create src/py_dvt_ate/server/tcp_server.py
+- Create src/py_dvt_ate/simulation/tcp_server.py
 - Define InstrumentServer class with asyncio
 - **Commit:** "Add async TCP server foundation"
 
@@ -261,7 +259,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 - **Commit:** "Implement TCP client handling"
 
 ### Task 8.3: Create server main entry point
-- Create src/py_dvt_ate/server/main.py
+- Create src/py_dvt_ate/simulation/server.py
 - Wire up physics engine and instruments
 - Add CLI command to start server
 - **Commit:** "Add simulation server entry point"
@@ -278,13 +276,13 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Create client-side communication.
 
 ### Task 9.1: Define transport protocol
-- Create src/py_dvt_ate/transport/__init__.py
+- Create src/py_dvt_ate/instruments/transport/__init__.py
-- Create src/py_dvt_ate/transport/base.py
+- Create src/py_dvt_ate/instruments/transport/base.py
 - Define Transport Protocol class
 - **Commit:** "Add transport protocol definition"
 
 ### Task 9.2: Implement TCP transport
-- Create src/py_dvt_ate/transport/tcp.py
+- Create src/py_dvt_ate/instruments/transport/tcp.py
 - Implement TCPTransport class
 - connect(), write(), read(), query() methods
 - **Commit:** "Implement TCP transport"
@@ -301,19 +299,19 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Create instrument drivers using transport.
 
 ### Task 10.1: Define driver base class
-- Create src/py_dvt_ate/drivers/__init__.py
+- Create src/py_dvt_ate/instruments/drivers/__init__.py
-- Create src/py_dvt_ate/drivers/base.py
+- Create src/py_dvt_ate/instruments/drivers/base.py
 - Define BaseDriver with transport dependency
 - **Commit:** "Add driver base class"
 
 ### Task 10.2: Implement thermal chamber driver
-- Create src/py_dvt_ate/drivers/thermal_chamber.py
+- Create src/py_dvt_ate/instruments/drivers/chamber.py
 - Methods map to SCPI commands
 - **Commit:** "Add thermal chamber driver"
 
 ### Task 10.3: Implement PSU and DMM drivers
-- Create src/py_dvt_ate/drivers/power_supply.py
+- Create src/py_dvt_ate/instruments/drivers/power_supply.py
-- Create src/py_dvt_ate/drivers/multimeter.py
+- Create src/py_dvt_ate/instruments/drivers/multimeter.py
 - **Commit:** "Add PSU and DMM drivers"
 
 ### Task 10.4: Add driver tests
@@ -323,32 +321,30 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 
 ---
 
-## Sprint 11: Hardware Abstraction Layer
+## Sprint 11: Instrument Interfaces
 
-**Goal:** Create HAL interfaces and implementations.
+**Goal:** Create instrument protocol interfaces and factory.
 
-### Task 11.1: Define HAL protocols
+### Task 11.1: Define instrument interface protocols
-- Create src/py_dvt_ate/hal/__init__.py
+- Create src/py_dvt_ate/instruments/interfaces.py
-- Create src/py_dvt_ate/hal/interfaces.py
+- Define IThermalChamber, IPowerSupply, IMultimeter protocols
-- Define IThermalChamber, IPowerSupply, IMultimeter
+- **Commit:** "Add instrument interface protocols"
-- **Commit:** "Add HAL protocol definitions"
 
-### Task 11.2: Implement HAL wrappers
+### Task 11.2: Ensure drivers implement interfaces
-- Create src/py_dvt_ate/hal/impl/__init__.py
+- Update drivers to satisfy Protocol interfaces
-- Create HAL implementation classes
+- Add type hints for interface compliance
-- Wrap drivers with HAL interface
+- **Commit:** "Implement instrument interfaces in drivers"
-- **Commit:** "Add HAL implementations"
 
 ### Task 11.3: Create instrument factory
-- Create src/py_dvt_ate/hal/factory.py
+- Create src/py_dvt_ate/instruments/factory.py
 - InstrumentSet dataclass
 - InstrumentFactory.create() method
 - **Commit:** "Add instrument factory"
 
-### Task 11.4: Add HAL tests
+### Task 11.4: Add instrument interface tests
-- Create tests/unit/test_hal.py
+- Create tests/unit/test_instruments.py
 - Test factory creates correct types
-- **Commit:** "Add HAL unit tests"
+- **Commit:** "Add instrument interface tests"
 
 ---
 
@@ -357,13 +353,12 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** YAML-based configuration.
 
 ### Task 12.1: Define config models
-- Create src/py_dvt_ate/config/__init__.py
+- Create src/py_dvt_ate/app/config.py
-- Create src/py_dvt_ate/config/models.py
+- Define Pydantic models for all config sections
-- Pydantic models for all config sections
 - **Commit:** "Add configuration Pydantic models"
 
 ### Task 12.2: Implement config loader
-- Create src/py_dvt_ate/config/loader.py
+- Add load_config() function to src/py_dvt_ate/app/config.py
 - Load YAML, validate with Pydantic
 - Environment variable overrides
 - **Commit:** "Implement configuration loader"
@@ -410,25 +405,25 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 **Goal:** Test execution orchestration.
 
 ### Task 14.1: Define test interface and models
-- Create src/py_dvt_ate/executive/__init__.py
+- Create src/py_dvt_ate/framework/__init__.py
-- Create src/py_dvt_ate/executive/models.py
+- Create src/py_dvt_ate/framework/context.py
 - TestStatus enum, TestContext, ITest protocol
-- **Commit:** "Add test executive models"
+- **Commit:** "Add test framework models"
 
 ### Task 14.2: Implement test logger
-- Create src/py_dvt_ate/executive/logger.py
+- Create src/py_dvt_ate/framework/logger.py
 - Log measurements and events
 - **Commit:** "Implement test logger"
 
 ### Task 14.3: Implement limit checker
-- Create src/py_dvt_ate/executive/limits.py
+- Create src/py_dvt_ate/framework/limits.py
 - Evaluate pass/fail against limits
 - **Commit:** "Implement limit checker"
 
-### Task 14.4: Implement test sequencer
+### Task 14.4: Implement test runner
-- Create src/py_dvt_ate/executive/sequencer.py
+- Create src/py_dvt_ate/framework/runner.py
 - Run tests, collect results
-- **Commit:** "Implement test sequencer"
+- **Commit:** "Implement test runner"
 
 ---
 
@@ -443,7 +438,7 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 - **Commit:** "Add DVT test base class"
 
 ### Task 15.2: Implement TempCo test
-- Create src/py_dvt_ate/tests/tempco.py
+- Create src/py_dvt_ate/tests/thermal/tempco.py
 - Temperature sweep logic
 - Vout measurement at each temperature
 - TempCo calculation
@@ -517,40 +512,38 @@ Each sprint is ~1-2 days of work, producing demonstrable progress.
 ## File Dependencies Map
 
 ```
-physics/models.py          → (none)
+simulation/physics/models.py         → (none)
-physics/dut/base.py        → models.py
+simulation/physics/models/base.py    → models.py
-physics/dut/ldo.py         → base.py, models.py
+simulation/physics/models/ldo.py     → base.py, models.py
-physics/thermal.py         → models.py
+simulation/physics/thermal.py        → models.py
-physics/engine.py          → models.py, thermal.py, dut/base.py
+simulation/physics/engine.py         → models.py, thermal.py, models/base.py
 
-dashboard/app.py           → physics/engine.py (Sprint 4, direct connection)
+app/dashboard/app.py                 → simulation/physics/engine.py (Sprint 4)
 
-instruments/scpi_parser.py → (none)
+instruments/scpi.py                  → (none)
-instruments/base.py        → scpi_parser.py
+simulation/virtual/base.py           → instruments/scpi.py
-instruments/*_sim.py       → base.py, physics/engine.py
+simulation/virtual/*.py              → base.py, simulation/physics/engine.py
 
-transport/base.py          → (none)
+instruments/transport/base.py        → (none)
-transport/tcp.py           → base.py
+instruments/transport/tcp.py         → base.py
 
-drivers/base.py            → transport/base.py
+instruments/drivers/base.py          → instruments/transport/base.py
-drivers/*.py               → base.py
+instruments/drivers/*.py             → base.py
 
-hal/interfaces.py          → (none)
+instruments/interfaces.py            → (none)
-hal/impl/*.py              → interfaces.py, drivers/*.py
+instruments/factory.py               → interfaces.py, drivers/*.py
-hal/factory.py             → interfaces.py, impl/*.py
 
-config/models.py           → (none)
+app/config.py                        → (none)
-config/loader.py           → models.py
 
 data/models.py                       → (none)
 data/repository.py                   → models.py
 
-executive/models.py        → hal/interfaces.py
+framework/context.py                 → instruments/interfaces.py
-executive/*.py             → models.py, data/repository.py
+framework/*.py                       → context.py, data/repository.py
 
-tests/*.py                 → executive/models.py, hal/interfaces.py
+tests/*.py                           → framework/context.py, instruments/interfaces.py
 
-dashboard/app.py           → hal/factory.py (Sprint 17, upgraded)
+app/dashboard/app.py                 → instruments/factory.py (Sprint 17, upgraded)
 ```
 
 ---
@@ -578,7 +571,7 @@ MAJOR.MINOR.PATCH[-PRERELEASE]
 | 3 | `v0.1.0-alpha.1` | Physics engine working | Pre-release |
 | 4 | `v0.1.0-alpha.2` | Visual demo (dashboard) | Pre-release |
 | 8 | `v0.1.0-alpha.3` | Network ready (TCP server) | Pre-release |
-| 11 | `v0.1.0-beta.1` | HAL complete | Pre-release |
+| 11 | `v0.1.0-beta.1` | Interfaces complete | Pre-release |
 | 15 | `v0.1.0-beta.2` | First DVT test runs | Pre-release |
 | 17 | `v0.1.0` | **MVP Complete** | Release |
 
@@ -644,7 +637,7 @@ Maintain `CHANGELOG.md` following [Keep a Changelog](https://keepachangelog.com/
 | 4 | `v0.1.0-alpha.2` | **Visual Demo!** | Interactive Streamlit showing physics |
 | 7 | - | Instruments Done | SCPI simulators respond to commands |
 | 8 | `v0.1.0-alpha.3` | Network Ready | TCP server accepts connections |
-| 11 | `v0.1.0-beta.1` | HAL Complete | Abstraction layer swappable |
+| 11 | `v0.1.0-beta.1` | Interfaces Complete | Instrument layer swappable |
 | 15 | `v0.1.0-beta.2` | First Test | TempCo characterisation runs |
 | 17 | `v0.1.0` | **MVP Complete** | Full end-to-end workflow |
 

pyproject.toml

@@ -40,9 +40,9 @@ dev = [
 ]
 
 [project.scripts]
-py-dvt-ate = "py_dvt_ate.cli.main:app"
+py-dvt-ate = "py_dvt_ate.app.cli:app"
-py-dvt-ate-server = "py_dvt_ate.server.main:main"
+py-dvt-ate-server = "py_dvt_ate.simulation.server:main"
-py-dvt-ate-dashboard = "py_dvt_ate.dashboard.app:main"
+py-dvt-ate-dashboard = "py_dvt_ate.app.dashboard.app:main"
 
 [build-system]
 requires = ["hatchling"]
@@ -86,5 +86,8 @@ ignore_missing_imports = true
 
 [tool.pytest.ini_options]
 testpaths = ["tests"]
-asyncio_mode = "auto"
 addopts = "-v --tb=short"
+
+[tool.pytest-asyncio]
+mode = "auto"
+default_fixture_loop_scope = "function"

src/py_dvt_ate/__init__.py

@@ -1,3 +1,3 @@
 """py_dvt_ate: Coupled Physics DVT Simulation Platform."""
 
-__version__ = "0.0.1"
+__version__ = "0.1.0-alpha.3"

src/py_dvt_ate/app/__init__.py

@@ -0,0 +1,5 @@
+"""Application entry points.
+
+Contains CLI, dashboard, and configuration loading for the
+py_dvt_ate application.
+"""

src/py_dvt_ate/app/cli.py

@@ -0,0 +1,87 @@
+"""Command-line interface for py_dvt_ate."""
+
+from typing import Annotated, Optional
+
+import typer
+
+from py_dvt_ate import __version__
+
+app = typer.Typer(
+    name="py-dvt-ate",
+    help="Coupled Physics DVT Simulation Platform",
+    add_completion=False,
+)
+
+
+def version_callback(value: bool) -> None:
+    """Print version and exit."""
+    if value:
+        typer.echo(f"py-dvt-ate version {__version__}")
+        raise typer.Exit()
+
+
+@app.callback()
+def main(
+    version: Annotated[
+        Optional[bool],
+        typer.Option(
+            "--version",
+            "-v",
+            help="Show version and exit.",
+            callback=version_callback,
+            is_eager=True,
+        ),
+    ] = None,
+) -> None:
+    """py-dvt-ate: Coupled Physics DVT Simulation Platform."""
+
+
+@app.command()
+def serve(
+    host: Annotated[
+        str,
+        typer.Option("--host", "-h", help="Host address to bind to."),
+    ] = "127.0.0.1",
+    chamber_port: Annotated[
+        int,
+        typer.Option("--chamber-port", help="Port for thermal chamber instrument."),
+    ] = 5000,
+    psu_port: Annotated[
+        int,
+        typer.Option("--psu-port", help="Port for power supply instrument."),
+    ] = 5001,
+    dmm_port: Annotated[
+        int,
+        typer.Option("--dmm-port", help="Port for multimeter instrument."),
+    ] = 5002,
+    physics_rate: Annotated[
+        float,
+        typer.Option("--physics-rate", help="Physics engine update rate in Hz."),
+    ] = 100.0,
+) -> None:
+    """Start the simulation server with virtual instruments.
+
+    Runs a TCP server hosting virtual SCPI instruments connected to a
+    shared physics engine. Each instrument listens on its own port.
+    """
+    from py_dvt_ate.simulation.server import main as run_server
+
+    typer.echo(f"Starting simulation server on {host}...")
+    typer.echo(f"  Thermal chamber: port {chamber_port}")
+    typer.echo(f"  Power supply:    port {psu_port}")
+    typer.echo(f"  Multimeter:      port {dmm_port}")
+    typer.echo(f"  Physics rate:    {physics_rate} Hz")
+    typer.echo("")
+    typer.echo("Press Ctrl+C to stop.")
+
+    run_server(
+        host=host,
+        chamber_port=chamber_port,
+        psu_port=psu_port,
+        dmm_port=dmm_port,
+        physics_rate=physics_rate,
+    )
+
+
+if __name__ == "__main__":
+    app()

src/py_dvt_ate/app/dashboard/__init__.py

@@ -0,0 +1,9 @@
+"""Streamlit dashboard for real-time monitoring.
+
+Provides visualisation of instrument status, test progress,
+and historical results.
+"""
+
+from py_dvt_ate.app.dashboard.app import main
+
+__all__ = ["main"]

src/py_dvt_ate/app/dashboard/app.py

@@ -0,0 +1,321 @@
+"""Streamlit dashboard application for physics simulation visualisation.
+
+This module provides an interactive dashboard for visualising the physics
+engine directly, demonstrating thermal-electrical coupling in real-time.
+"""
+
+import time
+from collections import deque
+from dataclasses import dataclass, field
+
+import streamlit as st
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+
+
+# History buffer size for charts
+HISTORY_SIZE = 500
+
+
+@dataclass
+class SimulationHistory:
+    """Stores time series data for visualisation."""
+
+    time: deque[float] = field(default_factory=lambda: deque(maxlen=HISTORY_SIZE))
+    chamber_temp: deque[float] = field(
+        default_factory=lambda: deque(maxlen=HISTORY_SIZE)
+    )
+    case_temp: deque[float] = field(default_factory=lambda: deque(maxlen=HISTORY_SIZE))
+    junction_temp: deque[float] = field(
+        default_factory=lambda: deque(maxlen=HISTORY_SIZE)
+    )
+    output_voltage: deque[float] = field(
+        default_factory=lambda: deque(maxlen=HISTORY_SIZE)
+    )
+    power_dissipation: deque[float] = field(
+        default_factory=lambda: deque(maxlen=HISTORY_SIZE)
+    )
+
+
+def init_session_state() -> None:
+    """Initialise Streamlit session state."""
+    if "engine" not in st.session_state:
+        st.session_state.engine = PhysicsEngine(update_rate_hz=100.0)
+    if "history" not in st.session_state:
+        st.session_state.history = SimulationHistory()
+    if "running" not in st.session_state:
+        st.session_state.running = False
+    if "last_update" not in st.session_state:
+        st.session_state.last_update = time.time()
+    # Note: time_multiplier, temp_setpoint, input_voltage, output_enabled,
+    # load_current are managed by their respective widgets via keys
+
+
+def step_simulation() -> None:
+    """Advance the simulation based on elapsed real time and multiplier."""
+    engine: PhysicsEngine = st.session_state.engine
+    history: SimulationHistory = st.session_state.history
+    multiplier: float = st.session_state.get("time_multiplier", 10)
+
+    # Calculate how much simulation time to advance
+    current_time = time.time()
+    elapsed_real = current_time - st.session_state.last_update
+    st.session_state.last_update = current_time
+
+    # Simulation time to advance (capped to prevent huge jumps)
+    sim_time_to_advance = min(elapsed_real * multiplier, 2.0)
+
+    # Calculate number of steps needed
+    steps = int(sim_time_to_advance / engine.dt)
+    steps = max(1, min(steps, 1000))  # Clamp between 1 and 1000 steps
+
+    for _ in range(steps):
+        engine.step()
+
+    # Record current state in history
+    thermal = engine.get_thermal_state()
+    electrical = engine.get_electrical_state()
+
+    history.time.append(thermal.timestamp)
+    history.chamber_temp.append(thermal.chamber_temperature)
+    history.case_temp.append(thermal.case_temperature)
+    history.junction_temp.append(thermal.junction_temperature)
+    history.output_voltage.append(electrical.output_voltage)
+    history.power_dissipation.append(electrical.power_dissipation)
+
+
+def sync_engine_from_session_state() -> None:
+    """Sync engine parameters from session state (called by fragment)."""
+    engine: PhysicsEngine = st.session_state.engine
+    engine.set_chamber_setpoint(st.session_state.get("temp_setpoint", 25.0))
+    engine.set_input_voltage(st.session_state.get("input_voltage", 5.0))
+    engine.set_output_enabled(st.session_state.get("output_enabled", False))
+    engine.set_load_current(st.session_state.get("load_current", 100.0) / 1000.0)
+
+
+def display_controls() -> None:
+    """Display simulation control panel in sidebar."""
+    st.sidebar.header("Simulation Controls")
+
+    # Start/Stop button
+    if st.session_state.running:
+        if st.sidebar.button(
+            "Stop Simulation", type="primary", use_container_width=True
+        ):
+            st.session_state.running = False
+    else:
+        if st.sidebar.button(
+            "Start Simulation", type="primary", use_container_width=True
+        ):
+            st.session_state.running = True
+            st.session_state.last_update = time.time()
+
+    # Reset button
+    if st.sidebar.button("Reset", use_container_width=True):
+        st.session_state.engine = PhysicsEngine(update_rate_hz=100.0)
+        st.session_state.history = SimulationHistory()
+        st.session_state.running = False
+        st.session_state.last_update = time.time()
+
+    st.sidebar.divider()
+
+    # Time multiplier
+    st.sidebar.subheader("Simulation Speed")
+    st.sidebar.select_slider(
+        "Time Multiplier",
+        options=[1, 2, 5, 10, 20, 50, 100],
+        value=10,
+        format_func=lambda x: f"{x}x",
+        key="time_multiplier",
+    )
+    st.sidebar.caption(
+        f"1 real second = {st.session_state.get('time_multiplier', 10)} simulation seconds"
+    )
+
+    st.sidebar.divider()
+
+    # Temperature setpoint
+    st.sidebar.subheader("Thermal Chamber")
+    st.sidebar.slider(
+        "Temperature Setpoint (C)",
+        min_value=-40.0,
+        max_value=125.0,
+        value=25.0,
+        step=5.0,
+        key="temp_setpoint",
+    )
+
+    st.sidebar.divider()
+
+    # Power supply controls
+    st.sidebar.subheader("Power Supply")
+    st.sidebar.slider(
+        "Input Voltage (V)",
+        min_value=0.0,
+        max_value=12.0,
+        value=5.0,
+        step=0.1,
+        key="input_voltage",
+    )
+
+    st.sidebar.toggle(
+        "Output Enabled",
+        value=False,
+        key="output_enabled",
+    )
+
+    st.sidebar.divider()
+
+    # Load controls
+    st.sidebar.subheader("Electronic Load")
+    st.sidebar.slider(
+        "Load Current (mA)",
+        min_value=0.0,
+        max_value=500.0,
+        value=100.0,
+        step=10.0,
+        key="load_current",
+    )
+
+
+@st.fragment(run_every=0.1)
+def simulation_display() -> None:
+    """Fragment that displays and updates simulation state."""
+    engine: PhysicsEngine = st.session_state.engine
+    history: SimulationHistory = st.session_state.history
+
+    # Sync engine parameters from UI controls
+    sync_engine_from_session_state()
+
+    # Step simulation if running
+    if st.session_state.running:
+        step_simulation()
+
+    # Get current state
+    thermal = engine.get_thermal_state()
+    electrical = engine.get_electrical_state()
+
+    # Current state metrics
+    st.subheader("Current State")
+    col1, col2, col3, col4 = st.columns(4)
+
+    with col1:
+        st.metric("Chamber Temp", f"{thermal.chamber_temperature:.2f} C")
+    with col2:
+        st.metric("Case Temp", f"{thermal.case_temperature:.2f} C")
+    with col3:
+        st.metric("Junction Temp", f"{thermal.junction_temperature:.2f} C")
+    with col4:
+        st.metric("Output Voltage", f"{electrical.output_voltage:.4f} V")
+
+    col5, col6, col7, col8 = st.columns(4)
+
+    with col5:
+        st.metric("Input Voltage", f"{electrical.input_voltage:.2f} V")
+    with col6:
+        st.metric("Load Current", f"{electrical.load_current * 1000:.1f} mA")
+    with col7:
+        st.metric("Power Diss.", f"{electrical.power_dissipation * 1000:.2f} mW")
+    with col8:
+        status = "Running" if st.session_state.running else "Stopped"
+        st.metric(
+            "Sim Time",
+            f"{engine.simulation_time:.1f} s",
+            delta=f"{status} @ {st.session_state.get('time_multiplier', 10):.0f}x",
+        )
+
+    # Temperature chart
+    st.subheader("Temperature History")
+    if len(history.time) < 2:
+        st.info("Start the simulation to see temperature data")
+    else:
+        chart_data = {
+            "Time (s)": list(history.time),
+            "Chamber": list(history.chamber_temp),
+            "Case": list(history.case_temp),
+            "Junction": list(history.junction_temp),
+        }
+        st.line_chart(
+            chart_data,
+            x="Time (s)",
+            y=["Chamber", "Case", "Junction"],
+            color=["#1f77b4", "#ff7f0e", "#d62728"],
+        )
+
+    # Self-heating demonstration
+    st.subheader("Self-Heating Demonstration")
+
+    delta_t_jc = thermal.junction_temperature - thermal.case_temperature
+    delta_t_ca = thermal.case_temperature - thermal.chamber_temperature
+
+    col1, col2 = st.columns(2)
+
+    with col1:
+        st.markdown("#### Self-Heating Analysis")
+        st.markdown(
+            f"""
+| Parameter | Value |
+|-----------|-------|
+| Junction-Case Rise (dT_jc) | **{delta_t_jc:.2f} C** |
+| Case-Ambient Rise (dT_ca) | **{delta_t_ca:.2f} C** |
+| Power Dissipation | {electrical.power_dissipation * 1000:.1f} mW |
+| theta_jc (junction-case) | 15 C/W |
+| theta_ca (case-ambient) | 5 C/W |
+"""
+        )
+        st.markdown(
+            """
+**Thermal Coupling:** The junction temperature rises above the case
+temperature due to power dissipation. This is governed by:
+
+`T_junction = T_case + P_diss x theta_jc`
+
+Try increasing the load current or input voltage to see
+self-heating effects!
+"""
+        )
+
+    with col2:
+        st.markdown("#### Power Dissipation")
+        if len(history.time) < 2:
+            st.info("Start the simulation to see power data")
+        else:
+            power_data = {
+                "Time (s)": list(history.time),
+                "Power (mW)": [p * 1000 for p in history.power_dissipation],
+            }
+            st.line_chart(
+                power_data,
+                x="Time (s)",
+                y="Power (mW)",
+                color="#2ca02c",
+            )
+
+
+def main() -> None:
+    """Main entry point for the Streamlit dashboard."""
+    st.set_page_config(
+        page_title="py-dvt-ate Virtual Lab Bench",
+        page_icon="🔬",
+        layout="wide",
+    )
+
+    st.title("py-dvt-ate Virtual Lab Bench")
+    st.markdown(
+        """
+        Interactive physics simulation demonstrating coupled thermal-electrical
+        behaviour of an LDO voltage regulator.
+        """
+    )
+
+    init_session_state()
+
+    # Sidebar controls (static - doesn't need fragment)
+    display_controls()
+
+    # Dynamic simulation display (uses fragment for smooth updates)
+    simulation_display()
+
+
+if __name__ == "__main__":
+    main()

src/py_dvt_ate/cli/__init__.py

@@ -1 +0,0 @@
-"""Command-line interface."""

src/py_dvt_ate/cli/main.py

@@ -1,40 +0,0 @@
-"""Command-line interface for py_dvt_ate."""
-
-from typing import Annotated, Optional
-
-import typer
-
-from py_dvt_ate import __version__
-
-app = typer.Typer(
-    name="py-dvt-ate",
-    help="Coupled Physics DVT Simulation Platform",
-    add_completion=False,
-)
-
-
-def version_callback(value: bool) -> None:
-    """Print version and exit."""
-    if value:
-        typer.echo(f"py-dvt-ate version {__version__}")
-        raise typer.Exit()
-
-
-@app.callback()
-def main(
-    version: Annotated[
-        Optional[bool],
-        typer.Option(
-            "--version",
-            "-v",
-            help="Show version and exit.",
-            callback=version_callback,
-            is_eager=True,
-        ),
-    ] = None,
-) -> None:
-    """py-dvt-ate: Coupled Physics DVT Simulation Platform."""
-
-
-if __name__ == "__main__":
-    app()

src/py_dvt_ate/config/__init__.py

@@ -1 +0,0 @@
-"""Configuration handling."""

src/py_dvt_ate/dashboard/__init__.py

@@ -1 +0,0 @@
-"""Streamlit dashboard."""

src/py_dvt_ate/drivers/__init__.py

@@ -1 +0,0 @@
-"""Instrument SCPI drivers."""

src/py_dvt_ate/executive/__init__.py

@@ -1 +0,0 @@
-"""Test execution framework."""

src/py_dvt_ate/framework/__init__.py

@@ -0,0 +1,5 @@
+"""Test execution framework.
+
+Provides test sequencing, measurement logging, limit checking,
+and runtime context management for DVT characterisation tests.
+"""

src/py_dvt_ate/hal/__init__.py

@@ -1 +0,0 @@
-"""Hardware Abstraction Layer."""

src/py_dvt_ate/hal/impl/__init__.py

@@ -1 +0,0 @@
-"""HAL implementations."""

src/py_dvt_ate/instruments/__init__.py

@@ -1 +1,9 @@
-"""Virtual instrument implementations."""
+"""Instrument control package.
+
+This package provides everything needed to communicate with lab instruments:
+- Protocol interfaces (IThermalChamber, IPowerSupply, IMultimeter)
+- SCPI command parsing
+- Transport layer (TCP, VISA)
+- Instrument drivers
+- Factory for creating configured instrument sets
+"""

src/py_dvt_ate/instruments/drivers/__init__.py

@@ -0,0 +1,5 @@
+"""SCPI driver implementations for lab instruments.
+
+Each driver translates high-level operations into SCPI commands
+and handles responses from instruments.
+"""

src/py_dvt_ate/instruments/scpi.py

@@ -0,0 +1,87 @@
+"""SCPI command parsing.
+
+This module provides SCPI (Standard Commands for Programmable Instruments)
+command parsing for instrument communication. It handles IEEE 488.2 common
+commands (*IDN?, *RST, etc.) and instrument-specific commands.
+"""
+
+from dataclasses import dataclass
+
+
+@dataclass
+class SCPICommand:
+    """Parsed SCPI command.
+
+    Attributes:
+        header: The command header (e.g., "TEMP:SETPOINT" or "*IDN").
+        arguments: List of command arguments (e.g., ["85.0"]).
+        is_query: True if the command ends with '?' (query command).
+    """
+
+    header: str
+    arguments: list[str]
+    is_query: bool
+
+    @property
+    def keyword(self) -> str:
+        """Return the command keyword without '?'.
+
+        For query commands like "TEMP:SETPOINT?", returns "TEMP:SETPOINT".
+        For regular commands like "VOLT", returns "VOLT".
+        """
+        return self.header.rstrip("?")
+
+
+class SCPIParser:
+    """Parse SCPI command strings.
+
+    Handles both IEEE 488.2 common commands (e.g., *IDN?, *RST) and
+    instrument-specific commands (e.g., VOLT 3.3, TEMP:SETPOINT?).
+
+    Examples:
+        >>> parser = SCPIParser()
+        >>> cmd = parser.parse("*IDN?")
+        >>> cmd.header, cmd.is_query
+        ('*IDN?', True)
+        >>> cmd = parser.parse("VOLT 3.3")
+        >>> cmd.header, cmd.arguments
+        ('VOLT', ['3.3'])
+    """
+
+    def parse(self, command_string: str) -> SCPICommand:
+        """Parse a SCPI command string.
+
+        Args:
+            command_string: The raw SCPI command string to parse.
+
+        Returns:
+            SCPICommand with parsed header, arguments, and query flag.
+
+        Examples:
+            "*IDN?" -> SCPICommand("*IDN?", [], True)
+            "VOLT 3.3" -> SCPICommand("VOLT", ["3.3"], False)
+            "TEMP:SETPOINT?" -> SCPICommand("TEMP:SETPOINT?", [], True)
+            "CONF:VOLT:DC 10,0.001" -> SCPICommand("CONF:VOLT:DC", ["10", "0.001"], False)
+        """
+        command_string = command_string.strip()
+        if not command_string:
+            return SCPICommand(header="", arguments=[], is_query=False)
+
+        # Split into header and arguments on first whitespace
+        parts = command_string.split(None, 1)
+        header = parts[0]
+        arguments: list[str] = []
+
+        if len(parts) > 1:
+            # Parse comma-separated arguments
+            arg_string = parts[1]
+            arguments = [arg.strip() for arg in arg_string.split(",")]
+
+        # Query is determined by whether the header ends with '?'
+        is_query = header.endswith("?")
+
+        return SCPICommand(
+            header=header,
+            arguments=arguments,
+            is_query=is_query,
+        )

src/py_dvt_ate/instruments/transport/__init__.py

@@ -0,0 +1,6 @@
+"""Transport layer for instrument communication.
+
+Provides connection abstractions for different backends:
+- TCP sockets (for simulation server)
+- PyVISA (for real instruments)
+"""

src/py_dvt_ate/physics/__init__.py

@@ -1 +0,0 @@
-"""Physics simulation engine."""

src/py_dvt_ate/physics/dut/__init__.py

@@ -1 +0,0 @@
-"""Device Under Test models."""

src/py_dvt_ate/reporting/__init__.py

@@ -0,0 +1,5 @@
+"""Report generation.
+
+Generates test reports from stored data in various formats
+including PDF and HTML.
+"""

src/py_dvt_ate/server/__init__.py

@@ -1 +0,0 @@
-"""Simulation server."""

src/py_dvt_ate/simulation/__init__.py

@@ -0,0 +1,10 @@
+"""Physics simulation package.
+
+Provides virtual instruments backed by a coupled thermal-electrical
+physics engine. Used for development and testing without real hardware.
+"""
+
+from py_dvt_ate.simulation.server import ServerConfig, SimulationServer
+from py_dvt_ate.simulation.tcp_server import InstrumentServer
+
+__all__ = ["InstrumentServer", "ServerConfig", "SimulationServer"]

src/py_dvt_ate/simulation/physics/__init__.py

@@ -0,0 +1,5 @@
+"""Physics engine for thermal-electrical simulation.
+
+Implements coupled thermal and electrical domain models with
+realistic time constants and temperature-dependent behaviour.
+"""

src/py_dvt_ate/simulation/physics/engine.py

@@ -0,0 +1,222 @@
+"""Physics engine for coupled thermal-electrical simulation.
+
+The physics engine maintains the simulation state and advances it
+in discrete time steps, modelling the thermal and electrical coupling
+between the DUT and its environment.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from py_dvt_ate.simulation.physics.state import ElectricalState, ThermalState
+from py_dvt_ate.simulation.physics.thermal import (
+    calculate_junction_temperature,
+    update_case_temperature,
+    update_temperature,
+)
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.physics.models.base import DUTModel
+
+
+class PhysicsEngine:
+    """Coupled thermal-electrical physics simulation.
+
+    Runs at a fixed timestep, updating thermal and electrical state
+    based on the DUT model and environmental conditions.
+
+    The simulation models:
+    - Chamber temperature approaching setpoint (first-order response)
+    - Case temperature driven by chamber and self-heating
+    - Junction temperature from case temperature and thermal resistance
+    - Electrical behaviour from the DUT model (temperature-dependent)
+
+    Attributes:
+        dt: Simulation timestep in seconds.
+    """
+
+    def __init__(
+        self,
+        update_rate_hz: float = 100.0,
+        dut_model: DUTModel | None = None,
+    ) -> None:
+        """Initialise the physics engine.
+
+        Args:
+            update_rate_hz: Simulation update rate in Hz. Defaults to 100.
+            dut_model: DUT model to use for electrical calculations.
+                       If None, a default LDO model will be used.
+        """
+        self.dt = 1.0 / update_rate_hz
+
+        # Lazily import to avoid circular dependencies
+        if dut_model is None:
+            from py_dvt_ate.simulation.physics.models.ldo import LDOModel
+
+            self._dut: DUTModel = LDOModel()
+        else:
+            self._dut = dut_model
+
+        # Thermal parameters
+        self._tau_chamber = 30.0  # seconds
+        self._tau_case = 5.0  # seconds
+        self._theta_jc = 15.0  # degC/W
+        self._theta_ca = 5.0  # degC/W
+
+        # State variables
+        self._t_setpoint = 25.0
+        self._t_chamber = 25.0
+        self._t_case = 25.0
+        self._v_in = 0.0
+        self._i_load = 0.0
+        self._output_enabled = False
+        self._sim_time = 0.0
+
+    def step(self) -> None:
+        """Advance simulation by one timestep.
+
+        Updates thermal and electrical state based on current conditions.
+        The thermal-electrical coupling works as follows:
+        1. Calculate current power dissipation from DUT model
+        2. Update chamber temperature towards setpoint
+        3. Update case temperature including self-heating
+        4. Advance simulation time
+        """
+        # Calculate power dissipation (uses current junction temperature estimate)
+        p_diss = self._calculate_power_dissipation()
+
+        # Update chamber temperature (first-order response to setpoint)
+        self._t_chamber = update_temperature(
+            current_temperature=self._t_chamber,
+            target_temperature=self._t_setpoint,
+            time_constant=self._tau_chamber,
+            dt=self.dt,
+        )
+
+        # Update case temperature (driven by chamber + self-heating)
+        self._t_case = update_case_temperature(
+            case_temperature=self._t_case,
+            ambient_temperature=self._t_chamber,
+            power_dissipation=p_diss,
+            time_constant=self._tau_case,
+            theta_ca=self._theta_ca,
+            dt=self.dt,
+        )
+
+        # Advance simulation time
+        self._sim_time += self.dt
+
+    def get_thermal_state(self) -> ThermalState:
+        """Get current thermal state snapshot.
+
+        Returns:
+            Immutable ThermalState with current temperatures.
+        """
+        p_diss = self._calculate_power_dissipation()
+        t_junction = calculate_junction_temperature(
+            case_temperature=self._t_case,
+            power_dissipation=p_diss,
+            theta_jc=self._theta_jc,
+        )
+
+        return ThermalState(
+            chamber_temperature=self._t_chamber,
+            case_temperature=self._t_case,
+            junction_temperature=t_junction,
+            timestamp=self._sim_time,
+        )
+
+    def get_electrical_state(self) -> ElectricalState:
+        """Get current electrical state snapshot.
+
+        Returns:
+            Immutable ElectricalState with current electrical values.
+        """
+        p_diss = self._calculate_power_dissipation()
+        t_junction = calculate_junction_temperature(
+            case_temperature=self._t_case,
+            power_dissipation=p_diss,
+            theta_jc=self._theta_jc,
+        )
+
+        if self._output_enabled:
+            v_out = self._dut.calculate_output_voltage(t_junction)
+            i_q = self._dut.calculate_quiescent_current(t_junction)
+            i_load = self._i_load
+        else:
+            v_out = 0.0
+            i_q = 0.0
+            i_load = 0.0
+
+        return ElectricalState(
+            input_voltage=self._v_in,
+            output_voltage=v_out,
+            load_current=i_load,
+            quiescent_current=i_q,
+            power_dissipation=p_diss,
+        )
+
+    def _calculate_power_dissipation(self) -> float:
+        """Calculate current power dissipation.
+
+        Uses the current case temperature as an approximation for junction
+        temperature in the power calculation. The true junction temperature
+        depends on power dissipation, creating a feedback loop that is
+        resolved iteratively through the simulation steps.
+
+        Returns:
+            Power dissipation in watts.
+        """
+        if not self._output_enabled:
+            return 0.0
+
+        # Use case temperature as junction estimate for power calculation
+        # This avoids circular dependency in the calculation
+        return self._dut.calculate_power_dissipation(
+            input_voltage=self._v_in,
+            load_current=self._i_load,
+            junction_temperature=self._t_case,
+        )
+
+    def set_chamber_setpoint(self, temperature: float) -> None:
+        """Set chamber target temperature.
+
+        Args:
+            temperature: Target temperature in degrees Celsius.
+        """
+        self._t_setpoint = temperature
+
+    def set_input_voltage(self, voltage: float) -> None:
+        """Set DUT input voltage.
+
+        Args:
+            voltage: Input voltage in volts.
+        """
+        self._v_in = voltage
+
+    def set_load_current(self, current: float) -> None:
+        """Set DUT load current.
+
+        Args:
+            current: Load current in amps.
+        """
+        self._i_load = current
+
+    def set_output_enabled(self, enabled: bool) -> None:
+        """Enable or disable DUT power.
+
+        Args:
+            enabled: True to enable output, False to disable.
+        """
+        self._output_enabled = enabled
+
+    @property
+    def simulation_time(self) -> float:
+        """Get current simulation time in seconds."""
+        return self._sim_time
+
+    @property
+    def is_output_enabled(self) -> bool:
+        """Check if DUT output is enabled."""
+        return self._output_enabled

src/py_dvt_ate/simulation/physics/models/__init__.py

@@ -0,0 +1,10 @@
+"""Device Under Test (DUT) models.
+
+Provides thermal and electrical models for various device types
+including LDO regulators, op-amps, and other components.
+"""
+
+from py_dvt_ate.simulation.physics.models.base import DUTModel
+from py_dvt_ate.simulation.physics.models.ldo import LDOModel, LDOParameters
+
+__all__ = ["DUTModel", "LDOModel", "LDOParameters"]

src/py_dvt_ate/simulation/physics/models/base.py

@@ -0,0 +1,61 @@
+"""Base protocol for Device Under Test (DUT) models.
+
+Defines the interface that all DUT models must implement to integrate
+with the physics engine.
+"""
+
+from typing import Protocol, runtime_checkable
+
+
+@runtime_checkable
+class DUTModel(Protocol):
+    """Protocol for DUT electrical/thermal models.
+
+    DUT models encapsulate the temperature-dependent electrical behaviour
+    of a device, enabling realistic simulation of thermal-electrical coupling.
+
+    All temperature parameters are in degrees Celsius.
+    All voltage parameters are in volts.
+    All current parameters are in amps.
+    All power parameters are in watts.
+    """
+
+    def calculate_output_voltage(self, junction_temperature: float) -> float:
+        """Calculate the output voltage at the given junction temperature.
+
+        Args:
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Output voltage in volts.
+        """
+        ...
+
+    def calculate_quiescent_current(self, junction_temperature: float) -> float:
+        """Calculate the quiescent current at the given junction temperature.
+
+        Args:
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Quiescent current in amps.
+        """
+        ...
+
+    def calculate_power_dissipation(
+        self,
+        input_voltage: float,
+        load_current: float,
+        junction_temperature: float,
+    ) -> float:
+        """Calculate the power dissipation for given operating conditions.
+
+        Args:
+            input_voltage: Input voltage in volts.
+            load_current: Load current in amps.
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Power dissipation in watts.
+        """
+        ...

src/py_dvt_ate/simulation/physics/models/ldo.py

@@ -0,0 +1,219 @@
+"""LDO (Low Dropout Regulator) DUT model.
+
+Implements temperature-dependent electrical behaviour for an LDO voltage
+regulator, including output voltage tempco, quiescent current variation,
+and power dissipation calculations.
+"""
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class LDOParameters:
+    """Configuration parameters for an LDO model.
+
+    All temperature coefficients are referenced to 25°C.
+
+    Attributes:
+        nominal_output_voltage: Nominal output voltage at 25°C in volts.
+        tempco_ppm_per_c: Output voltage temperature coefficient in ppm/°C.
+        quiescent_current_a: Quiescent current at 25°C in amps.
+        quiescent_current_tempco: Quiescent current temperature coefficient (1/°C).
+        dropout_voltage: Dropout voltage at 25°C in volts.
+        max_output_current: Maximum output current in amps.
+    """
+
+    nominal_output_voltage: float = 3.3
+    tempco_ppm_per_c: float = 50.0
+    quiescent_current_a: float = 50e-6  # 50 µA
+    quiescent_current_tempco: float = 0.003  # 0.3%/°C
+    dropout_voltage: float = 0.3
+    max_output_current: float = 0.5
+
+
+# Reference temperature for all calculations
+REFERENCE_TEMPERATURE_C = 25.0
+
+
+class LDOModel:
+    """Temperature-dependent LDO voltage regulator model.
+
+    Models the electrical behaviour of a linear voltage regulator with:
+    - Output voltage that varies with temperature (tempco in ppm/°C)
+    - Quiescent current that varies with temperature
+    - Dropout voltage that increases with temperature
+    - Power dissipation from (Vin - Vout) × Iload + Vin × Iq
+
+    This class implements the DUTModel protocol.
+    """
+
+    def __init__(
+        self,
+        params: LDOParameters | None = None,
+        input_voltage: float = 5.0,
+        load_current: float = 0.0,
+    ) -> None:
+        """Initialise the LDO model.
+
+        Args:
+            params: LDO parameters. Uses defaults if None.
+            input_voltage: Initial input voltage in volts.
+            load_current: Initial load current in amps.
+        """
+        self._params = params or LDOParameters()
+        self._input_voltage = input_voltage
+        self._load_current = load_current
+
+    @property
+    def params(self) -> LDOParameters:
+        """Get the LDO parameters."""
+        return self._params
+
+    @property
+    def input_voltage(self) -> float:
+        """Get the current input voltage."""
+        return self._input_voltage
+
+    @input_voltage.setter
+    def input_voltage(self, value: float) -> None:
+        """Set the input voltage."""
+        self._input_voltage = value
+
+    @property
+    def load_current(self) -> float:
+        """Get the current load current."""
+        return self._load_current
+
+    @load_current.setter
+    def load_current(self, value: float) -> None:
+        """Set the load current."""
+        self._load_current = value
+
+    def calculate_output_voltage(self, junction_temperature: float) -> float:
+        """Calculate the output voltage at the given junction temperature.
+
+        Implements: V_out(T) = V_nom × (1 + TC_vout × (T - 25) × 1e-6)
+
+        The output voltage is clamped to not exceed (Vin - Vdropout) when
+        the regulator is in dropout.
+
+        Args:
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Output voltage in volts.
+        """
+        delta_t = junction_temperature - REFERENCE_TEMPERATURE_C
+        tempco_factor = 1.0 + self._params.tempco_ppm_per_c * delta_t * 1e-6
+
+        ideal_vout = self._params.nominal_output_voltage * tempco_factor
+
+        # Calculate dropout voltage at temperature
+        v_dropout = self._calculate_dropout_voltage(junction_temperature)
+
+        # Clamp output to not exceed (Vin - Vdropout)
+        max_vout = max(0.0, self._input_voltage - v_dropout)
+
+        return min(ideal_vout, max_vout)
+
+    def calculate_quiescent_current(self, junction_temperature: float) -> float:
+        """Calculate the quiescent current at the given junction temperature.
+
+        Implements: I_q(T) = I_q_25 × (1 + TC_iq × (T - 25))
+
+        Args:
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Quiescent current in amps.
+        """
+        delta_t = junction_temperature - REFERENCE_TEMPERATURE_C
+        tempco_factor = 1.0 + self._params.quiescent_current_tempco * delta_t
+
+        return self._params.quiescent_current_a * tempco_factor
+
+    def calculate_power_dissipation(
+        self,
+        input_voltage: float,
+        load_current: float,
+        junction_temperature: float,
+    ) -> float:
+        """Calculate the power dissipation for given operating conditions.
+
+        Implements: P_diss = (V_in - V_out) × I_load + V_in × I_q
+
+        The power dissipation comes from:
+        - Voltage drop across the pass element times load current
+        - Quiescent current times input voltage
+
+        Args:
+            input_voltage: Input voltage in volts.
+            load_current: Load current in amps.
+            junction_temperature: DUT junction temperature in degrees Celsius.
+
+        Returns:
+            Power dissipation in watts.
+        """
+        # Temporarily set input voltage for output voltage calculation
+        original_vin = self._input_voltage
+        self._input_voltage = input_voltage
+
+        try:
+            v_out = self.calculate_output_voltage(junction_temperature)
+            i_q = self.calculate_quiescent_current(junction_temperature)
+
+            # Power in pass element
+            p_pass = (input_voltage - v_out) * load_current
+
+            # Power from quiescent current
+            p_quiescent = input_voltage * i_q
+
+            return p_pass + p_quiescent
+        finally:
+            self._input_voltage = original_vin
+
+    def _calculate_dropout_voltage(self, junction_temperature: float) -> float:
+        """Calculate the dropout voltage at the given temperature.
+
+        Implements: V_do(T) = V_do_25 × (T_K / 300)^1.5
+
+        where T_K is the temperature in Kelvin.
+
+        Dropout voltage increases with temperature due to increased
+        resistance of the pass element.
+
+        Args:
+            junction_temperature: Junction temperature in degrees Celsius.
+
+        Returns:
+            Dropout voltage in volts.
+        """
+        # Convert to Kelvin
+        t_kelvin = junction_temperature + 273.15
+
+        # Temperature ratio (reference is approximately 300K ≈ 27°C)
+        temp_ratio = t_kelvin / 300.0
+
+        return self._params.dropout_voltage * (temp_ratio**1.5)
+
+    def is_in_dropout(self, junction_temperature: float) -> bool:
+        """Check if the LDO is in dropout at current operating point.
+
+        The LDO is in dropout when the input voltage minus dropout voltage
+        is less than the nominal output voltage.
+
+        Args:
+            junction_temperature: Junction temperature in degrees Celsius.
+
+        Returns:
+            True if in dropout, False otherwise.
+        """
+        v_dropout = self._calculate_dropout_voltage(junction_temperature)
+        headroom = self._input_voltage - v_dropout
+
+        # Get the ideal (temperature-adjusted) output voltage
+        delta_t = junction_temperature - REFERENCE_TEMPERATURE_C
+        tempco_factor = 1.0 + self._params.tempco_ppm_per_c * delta_t * 1e-6
+        ideal_vout = self._params.nominal_output_voltage * tempco_factor
+
+        return headroom < ideal_vout

src/py_dvt_ate/simulation/physics/state.py

@@ -0,0 +1,48 @@
+"""Physics state dataclasses for thermal-electrical simulation.
+
+These immutable state snapshots represent the simulation state at a point in time.
+"""
+
+from dataclasses import dataclass
+
+
+@dataclass(frozen=True)
+class ThermalState:
+    """Immutable thermal state snapshot.
+
+    Represents the thermal conditions of the DUT and its environment
+    at a specific point in simulation time.
+
+    Attributes:
+        chamber_temperature: Chamber air temperature in degrees Celsius.
+        case_temperature: DUT case/package temperature in degrees Celsius.
+        junction_temperature: DUT junction/die temperature in degrees Celsius.
+        timestamp: Simulation time in seconds since start.
+    """
+
+    chamber_temperature: float
+    case_temperature: float
+    junction_temperature: float
+    timestamp: float
+
+
+@dataclass(frozen=True)
+class ElectricalState:
+    """Immutable electrical state snapshot.
+
+    Represents the electrical conditions of the DUT at a specific
+    point in simulation time.
+
+    Attributes:
+        input_voltage: DUT input voltage in volts.
+        output_voltage: DUT output voltage in volts.
+        load_current: Load current drawn from DUT in amps.
+        quiescent_current: DUT quiescent/bias current in amps.
+        power_dissipation: Total power dissipated by DUT in watts.
+    """
+
+    input_voltage: float
+    output_voltage: float
+    load_current: float
+    quiescent_current: float
+    power_dissipation: float

src/py_dvt_ate/simulation/physics/thermal.py

@@ -0,0 +1,193 @@
+"""Thermal calculation functions for physics simulation.
+
+Pure functions implementing first-order thermal response calculations
+for the coupled thermal-electrical simulation.
+
+All temperatures are in degrees Celsius.
+All time values are in seconds.
+All power values are in watts.
+All thermal resistances are in degrees Celsius per watt (°C/W).
+"""
+
+
+def calculate_temperature_derivative(
+    current_temperature: float,
+    target_temperature: float,
+    time_constant: float,
+) -> float:
+    """Calculate the rate of temperature change for first-order response.
+
+    Implements: dT/dt = (T_target - T_current) / τ
+
+    Args:
+        current_temperature: Current temperature in degrees Celsius.
+        target_temperature: Target temperature in degrees Celsius.
+        time_constant: Thermal time constant in seconds.
+
+    Returns:
+        Rate of temperature change in degrees Celsius per second.
+
+    Raises:
+        ValueError: If time_constant is not positive.
+    """
+    if time_constant <= 0:
+        msg = f"Time constant must be positive, got {time_constant}"
+        raise ValueError(msg)
+
+    return (target_temperature - current_temperature) / time_constant
+
+
+def update_temperature(
+    current_temperature: float,
+    target_temperature: float,
+    time_constant: float,
+    dt: float,
+) -> float:
+    """Calculate new temperature after a time step using Euler integration.
+
+    Args:
+        current_temperature: Current temperature in degrees Celsius.
+        target_temperature: Target temperature in degrees Celsius.
+        time_constant: Thermal time constant in seconds.
+        dt: Time step in seconds.
+
+    Returns:
+        New temperature in degrees Celsius after the time step.
+
+    Raises:
+        ValueError: If time_constant or dt is not positive.
+    """
+    if dt <= 0:
+        msg = f"Time step must be positive, got {dt}"
+        raise ValueError(msg)
+
+    derivative = calculate_temperature_derivative(
+        current_temperature, target_temperature, time_constant
+    )
+    return current_temperature + derivative * dt
+
+
+def calculate_case_temperature_derivative(
+    case_temperature: float,
+    ambient_temperature: float,
+    power_dissipation: float,
+    time_constant: float,
+    theta_ca: float,
+) -> float:
+    """Calculate rate of case temperature change including self-heating.
+
+    Implements: dT_case/dt = (T_ambient - T_case + P_diss × θ_ca) / τ_case
+
+    The case temperature is driven by:
+    - Convection/conduction to ambient (chamber) temperature
+    - Self-heating from power dissipation through case-to-ambient thermal resistance
+
+    Args:
+        case_temperature: Current case temperature in degrees Celsius.
+        ambient_temperature: Ambient (chamber) temperature in degrees Celsius.
+        power_dissipation: Power dissipated by the device in watts.
+        time_constant: Case thermal time constant in seconds.
+        theta_ca: Thermal resistance from case to ambient in °C/W.
+
+    Returns:
+        Rate of case temperature change in degrees Celsius per second.
+
+    Raises:
+        ValueError: If time_constant is not positive.
+    """
+    if time_constant <= 0:
+        msg = f"Time constant must be positive, got {time_constant}"
+        raise ValueError(msg)
+
+    # The effective target includes self-heating contribution
+    thermal_drive = ambient_temperature - case_temperature + power_dissipation * theta_ca
+    return thermal_drive / time_constant
+
+
+def update_case_temperature(
+    case_temperature: float,
+    ambient_temperature: float,
+    power_dissipation: float,
+    time_constant: float,
+    theta_ca: float,
+    dt: float,
+) -> float:
+    """Calculate new case temperature after a time step.
+
+    Args:
+        case_temperature: Current case temperature in degrees Celsius.
+        ambient_temperature: Ambient (chamber) temperature in degrees Celsius.
+        power_dissipation: Power dissipated by the device in watts.
+        time_constant: Case thermal time constant in seconds.
+        theta_ca: Thermal resistance from case to ambient in °C/W.
+        dt: Time step in seconds.
+
+    Returns:
+        New case temperature in degrees Celsius after the time step.
+
+    Raises:
+        ValueError: If time_constant or dt is not positive.
+    """
+    if dt <= 0:
+        msg = f"Time step must be positive, got {dt}"
+        raise ValueError(msg)
+
+    derivative = calculate_case_temperature_derivative(
+        case_temperature,
+        ambient_temperature,
+        power_dissipation,
+        time_constant,
+        theta_ca,
+    )
+    return case_temperature + derivative * dt
+
+
+def calculate_junction_temperature(
+    case_temperature: float,
+    power_dissipation: float,
+    theta_jc: float,
+) -> float:
+    """Calculate junction temperature from case temperature and power.
+
+    The junction temperature is assumed to respond instantaneously to
+    changes in case temperature and power dissipation (no thermal mass
+    at the die level for this simplified model).
+
+    Implements: T_junction = T_case + P_diss × θ_jc
+
+    Args:
+        case_temperature: Case temperature in degrees Celsius.
+        power_dissipation: Power dissipated by the device in watts.
+        theta_jc: Thermal resistance from junction to case in °C/W.
+
+    Returns:
+        Junction temperature in degrees Celsius.
+    """
+    return case_temperature + power_dissipation * theta_jc
+
+
+def calculate_steady_state_junction_temperature(
+    ambient_temperature: float,
+    power_dissipation: float,
+    theta_jc: float,
+    theta_ca: float,
+) -> float:
+    """Calculate the steady-state junction temperature.
+
+    At steady state, the case temperature reaches equilibrium where
+    the heat flow through θ_ca equals the power dissipation.
+
+    T_case_ss = T_ambient + P_diss × θ_ca
+    T_junction_ss = T_case_ss + P_diss × θ_jc
+                  = T_ambient + P_diss × (θ_jc + θ_ca)
+
+    Args:
+        ambient_temperature: Ambient (chamber) temperature in degrees Celsius.
+        power_dissipation: Power dissipated by the device in watts.
+        theta_jc: Thermal resistance from junction to case in °C/W.
+        theta_ca: Thermal resistance from case to ambient in °C/W.
+
+    Returns:
+        Steady-state junction temperature in degrees Celsius.
+    """
+    return ambient_temperature + power_dissipation * (theta_jc + theta_ca)

src/py_dvt_ate/simulation/server.py

@@ -0,0 +1,240 @@
+"""Simulation server entry point.
+
+This module provides the main entry point for running the simulation server
+with all virtual instruments wired to a shared physics engine.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+import signal
+from dataclasses import dataclass
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.tcp_server import InstrumentServer
+from py_dvt_ate.simulation.virtual.chamber import ThermalChamberSim
+from py_dvt_ate.simulation.virtual.multimeter import MultimeterSim
+from py_dvt_ate.simulation.virtual.power_supply import PowerSupplySim
+
+logger = logging.getLogger(__name__)
+
+
+@dataclass
+class ServerConfig:
+    """Configuration for the simulation server.
+
+    Attributes:
+        host: Host address to bind to.
+        chamber_port: Port for thermal chamber instrument.
+        psu_port: Port for power supply instrument.
+        dmm_port: Port for multimeter instrument.
+        physics_rate_hz: Physics engine update rate in Hz.
+    """
+
+    host: str = "127.0.0.1"
+    chamber_port: int = 5000
+    psu_port: int = 5001
+    dmm_port: int = 5002
+    physics_rate_hz: float = 100.0
+
+
+class SimulationServer:
+    """Complete simulation server with physics engine and instruments.
+
+    Creates a physics engine and wires it to all virtual instruments,
+    then exposes them over TCP for client access.
+    """
+
+    def __init__(self, config: ServerConfig | None = None) -> None:
+        """Initialise the simulation server.
+
+        Args:
+            config: Server configuration. Uses defaults if not provided.
+        """
+        self._config = config or ServerConfig()
+        self._physics_engine: PhysicsEngine | None = None
+        self._instrument_server: InstrumentServer | None = None
+        self._physics_task: asyncio.Task[None] | None = None
+        self._running = False
+
+    @property
+    def is_running(self) -> bool:
+        """Check if server is currently running."""
+        return self._running
+
+    @property
+    def physics_engine(self) -> PhysicsEngine | None:
+        """Get the physics engine instance."""
+        return self._physics_engine
+
+    def _setup(self) -> None:
+        """Create and wire up all components."""
+        # Create physics engine
+        self._physics_engine = PhysicsEngine(
+            update_rate_hz=self._config.physics_rate_hz
+        )
+
+        # Create instruments connected to physics engine
+        chamber = ThermalChamberSim(self._physics_engine)
+        psu = PowerSupplySim(self._physics_engine)
+        dmm = MultimeterSim(self._physics_engine)
+
+        # Create TCP server and register instruments
+        self._instrument_server = InstrumentServer(host=self._config.host)
+        self._instrument_server.register_instrument(self._config.chamber_port, chamber)
+        self._instrument_server.register_instrument(self._config.psu_port, psu)
+        self._instrument_server.register_instrument(self._config.dmm_port, dmm)
+
+        logger.info(
+            "Simulation server configured: chamber=%d, psu=%d, dmm=%d",
+            self._config.chamber_port,
+            self._config.psu_port,
+            self._config.dmm_port,
+        )
+
+    async def _run_physics(self) -> None:
+        """Run the physics engine simulation loop."""
+        if self._physics_engine is None:
+            return
+
+        dt = self._physics_engine.dt
+
+        while self._running:
+            self._physics_engine.step()
+            # Sleep for the physics timestep
+            await asyncio.sleep(dt)
+
+    async def start(self) -> None:
+        """Start the simulation server.
+
+        Sets up all components and starts the TCP server and physics engine.
+
+        Raises:
+            RuntimeError: If server is already running.
+        """
+        if self._running:
+            raise RuntimeError("Server is already running")
+
+        self._setup()
+        self._running = True
+
+        # Start TCP server
+        if self._instrument_server is not None:
+            await self._instrument_server.start()
+
+        # Start physics engine loop
+        self._physics_task = asyncio.create_task(self._run_physics())
+
+        logger.info("Simulation server started")
+
+    async def stop(self) -> None:
+        """Stop the simulation server."""
+        if not self._running:
+            return
+
+        self._running = False
+
+        # Cancel physics loop
+        if self._physics_task is not None:
+            self._physics_task.cancel()
+            try:
+                await self._physics_task
+            except asyncio.CancelledError:
+                pass
+            self._physics_task = None
+
+        # Stop TCP server
+        if self._instrument_server is not None:
+            await self._instrument_server.stop()
+            self._instrument_server = None
+
+        self._physics_engine = None
+        logger.info("Simulation server stopped")
+
+    async def serve_forever(self) -> None:
+        """Start the server and run until cancelled."""
+        await self.start()
+        try:
+            # Wait for the physics task (which runs until cancelled)
+            if self._physics_task is not None:
+                await self._physics_task
+        except asyncio.CancelledError:
+            pass
+        finally:
+            await self.stop()
+
+
+async def run_server(config: ServerConfig | None = None) -> None:
+    """Run the simulation server with signal handling.
+
+    This is the main entry point for running the server. It sets up
+    signal handlers for graceful shutdown.
+
+    Args:
+        config: Server configuration. Uses defaults if not provided.
+    """
+    server = SimulationServer(config)
+
+    # Set up signal handlers for graceful shutdown
+    loop = asyncio.get_running_loop()
+    stop_event = asyncio.Event()
+
+    def signal_handler() -> None:
+        logger.info("Shutdown signal received")
+        stop_event.set()
+
+    # Register signal handlers (Unix-style, may not work on all Windows)
+    try:
+        for sig in (signal.SIGINT, signal.SIGTERM):
+            loop.add_signal_handler(sig, signal_handler)
+    except NotImplementedError:
+        # Windows doesn't support add_signal_handler
+        pass
+
+    try:
+        await server.start()
+        logger.info("Simulation server running. Press Ctrl+C to stop.")
+
+        # Wait for stop signal
+        await stop_event.wait()
+    except KeyboardInterrupt:
+        logger.info("Keyboard interrupt received")
+    finally:
+        await server.stop()
+
+
+def main(
+    host: str = "127.0.0.1",
+    chamber_port: int = 5000,
+    psu_port: int = 5001,
+    dmm_port: int = 5002,
+    physics_rate: float = 100.0,
+) -> None:
+    """Run the simulation server from command line.
+
+    Args:
+        host: Host address to bind to.
+        chamber_port: Port for thermal chamber.
+        psu_port: Port for power supply.
+        dmm_port: Port for multimeter.
+        physics_rate: Physics engine update rate in Hz.
+    """
+    logging.basicConfig(
+        level=logging.INFO,
+        format="%(asctime)s - %(name)s - %(levelname)s - %(message)s",
+    )
+
+    config = ServerConfig(
+        host=host,
+        chamber_port=chamber_port,
+        psu_port=psu_port,
+        dmm_port=dmm_port,
+        physics_rate_hz=physics_rate,
+    )
+
+    asyncio.run(run_server(config))
+
+
+if __name__ == "__main__":
+    main()

src/py_dvt_ate/simulation/tcp_server.py

@@ -0,0 +1,212 @@
+"""Async TCP server for exposing virtual instruments over network.
+
+This module provides the InstrumentServer class that hosts virtual SCPI
+instruments over TCP, allowing client applications to communicate using
+standard SCPI commands over a network connection.
+"""
+
+from __future__ import annotations
+
+import asyncio
+import logging
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.virtual.base import BaseInstrument
+
+# Re-export for type checking - actual import happens at runtime via registration
+__all__ = ["InstrumentServer"]
+
+logger = logging.getLogger(__name__)
+
+
+class InstrumentServer:
+    """Async TCP server hosting virtual SCPI instruments.
+
+    Each instrument is assigned a port. Clients connect via TCP and send
+    SCPI commands as newline-terminated strings. Responses are also
+    newline-terminated.
+
+    Attributes:
+        host: Host address to bind to.
+    """
+
+    def __init__(self, host: str = "127.0.0.1") -> None:
+        """Initialise the instrument server.
+
+        Args:
+            host: Host address to bind to. Defaults to localhost.
+        """
+        self._host = host
+        self._instruments: dict[int, BaseInstrument] = {}
+        self._servers: list[asyncio.Server] = []
+        self._running = False
+
+    @property
+    def host(self) -> str:
+        """Get the host address."""
+        return self._host
+
+    @property
+    def is_running(self) -> bool:
+        """Check if server is currently running."""
+        return self._running
+
+    def register_instrument(self, port: int, instrument: BaseInstrument) -> None:
+        """Register an instrument to be served on a specific port.
+
+        Args:
+            port: TCP port number to serve the instrument on.
+            instrument: Virtual instrument to serve.
+
+        Raises:
+            ValueError: If port is already registered.
+            RuntimeError: If server is already running.
+        """
+        if self._running:
+            raise RuntimeError("Cannot register instruments while server is running")
+
+        if port in self._instruments:
+            raise ValueError(f"Port {port} is already registered")
+
+        self._instruments[port] = instrument
+        logger.info(
+            "Registered %s on port %d",
+            instrument.__class__.__name__,
+            port,
+        )
+
+    def get_instrument(self, port: int) -> BaseInstrument | None:
+        """Get the instrument registered on a port.
+
+        Args:
+            port: Port number to look up.
+
+        Returns:
+            Registered instrument, or None if port not registered.
+        """
+        return self._instruments.get(port)
+
+    @property
+    def registered_ports(self) -> list[int]:
+        """Get list of registered port numbers."""
+        return list(self._instruments.keys())
+
+    async def start(self) -> None:
+        """Start the server and begin listening on all registered ports.
+
+        Creates a TCP server for each registered instrument port.
+
+        Raises:
+            RuntimeError: If server is already running or no instruments registered.
+        """
+        if self._running:
+            raise RuntimeError("Server is already running")
+
+        if not self._instruments:
+            raise RuntimeError("No instruments registered")
+
+        self._running = True
+
+        for port, instrument in self._instruments.items():
+            server = await asyncio.start_server(
+                lambda r, w, inst=instrument, p=port: self._handle_client(r, w, inst, p),
+                self._host,
+                port,
+            )
+            self._servers.append(server)
+            logger.info(
+                "Started server for %s on %s:%d",
+                instrument.__class__.__name__,
+                self._host,
+                port,
+            )
+
+    async def stop(self) -> None:
+        """Stop the server and close all connections."""
+        if not self._running:
+            return
+
+        for server in self._servers:
+            server.close()
+            await server.wait_closed()
+
+        self._servers.clear()
+        self._running = False
+        logger.info("Server stopped")
+
+    async def serve_forever(self) -> None:
+        """Start the server and run until cancelled.
+
+        This is a convenience method that starts the server and blocks
+        until the server is stopped or cancelled.
+        """
+        await self.start()
+        try:
+            # Keep running until cancelled
+            await asyncio.gather(
+                *[server.serve_forever() for server in self._servers]
+            )
+        finally:
+            await self.stop()
+
+    async def _handle_client(
+        self,
+        reader: asyncio.StreamReader,
+        writer: asyncio.StreamWriter,
+        instrument: BaseInstrument,
+        port: int,
+    ) -> None:
+        """Handle a client connection.
+
+        Reads SCPI commands (newline-terminated), processes them through
+        the instrument, and sends back responses (newline-terminated).
+
+        Args:
+            reader: Stream reader for incoming data.
+            writer: Stream writer for outgoing data.
+            instrument: The instrument to process commands.
+            port: Port number for logging.
+        """
+        addr = writer.get_extra_info("peername")
+        logger.info("Client connected to port %d from %s", port, addr)
+
+        try:
+            while True:
+                # Read until newline (SCPI line terminator)
+                data = await reader.readline()
+
+                if not data:
+                    # Client disconnected
+                    break
+
+                # Decode and strip whitespace
+                command = data.decode("utf-8").strip()
+
+                if not command:
+                    continue
+
+                logger.debug("Port %d received: %s", port, command)
+
+                # Process command through instrument
+                response = instrument.process(command)
+
+                # Send response with newline terminator
+                if response:
+                    writer.write(f"{response}\n".encode("utf-8"))
+                    await writer.drain()
+                    logger.debug("Port %d sent: %s", port, response)
+
+        except asyncio.CancelledError:
+            logger.debug("Client handler cancelled for port %d", port)
+        except ConnectionResetError:
+            logger.debug("Client connection reset on port %d", port)
+        except Exception as e:
+            logger.error("Error handling client on port %d: %s", port, e)
+        finally:
+            writer.close()
+            try:
+                await writer.wait_closed()
+            except Exception:
+                pass
+            logger.info("Client disconnected from port %d", port)

src/py_dvt_ate/simulation/virtual/__init__.py

@@ -0,0 +1,5 @@
+"""Virtual instrument implementations.
+
+SCPI-compliant virtual instruments that respond like real hardware
+but are backed by the physics simulation engine.
+"""

src/py_dvt_ate/simulation/virtual/base.py

@@ -0,0 +1,156 @@
+"""Base class for virtual instrument simulators.
+
+This module provides the foundation for implementing SCPI-based virtual
+instruments that can be exposed over TCP for hardware abstraction testing.
+"""
+
+from __future__ import annotations
+
+from abc import ABC, abstractmethod
+from collections.abc import Callable
+from typing import TYPE_CHECKING
+
+from py_dvt_ate.instruments.scpi import SCPICommand, SCPIParser
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+
+
+# Type alias for command handlers
+CommandHandler = Callable[[SCPICommand], str]
+
+
+class BaseInstrument(ABC):
+    """Abstract base class for virtual SCPI instruments.
+
+    Provides common functionality for SCPI command parsing and dispatch.
+    Subclasses should register command handlers using the register_command
+    method or by overriding _setup_commands.
+
+    Attributes:
+        manufacturer: Instrument manufacturer name for *IDN? response.
+        model: Instrument model name for *IDN? response.
+        serial_number: Instrument serial number for *IDN? response.
+        firmware_version: Firmware version for *IDN? response.
+    """
+
+    manufacturer: str = "PyDVTATE"
+    model: str = "Virtual Instrument"
+    serial_number: str = "SIM001"
+    firmware_version: str = "1.0.0"
+
+    def __init__(self, physics_engine: PhysicsEngine | None = None) -> None:
+        """Initialise the base instrument.
+
+        Args:
+            physics_engine: Reference to physics engine for simulation state.
+                           May be None for standalone operation.
+        """
+        self._physics_engine = physics_engine
+        self._parser = SCPIParser()
+        self._handlers: dict[str, CommandHandler] = {}
+        self._setup_common_commands()
+        self._setup_commands()
+
+    def _setup_common_commands(self) -> None:
+        """Register IEEE 488.2 common commands."""
+        self.register_command("*IDN", self._handle_idn)
+        self.register_command("*RST", self._handle_rst)
+        self.register_command("*CLS", self._handle_cls)
+        self.register_command("*OPC", self._handle_opc)
+
+    @abstractmethod
+    def _setup_commands(self) -> None:
+        """Register instrument-specific command handlers.
+
+        Subclasses must implement this method to register their
+        SCPI command handlers using register_command().
+        """
+
+    def register_command(self, keyword: str, handler: CommandHandler) -> None:
+        """Register a handler for a SCPI command keyword.
+
+        Args:
+            keyword: The command keyword (e.g., "TEMP:SETPOINT").
+                    For commands that support both set and query forms,
+                    register the base keyword without '?'.
+            handler: Callable that takes SCPICommand and returns response string.
+        """
+        self._handlers[keyword.upper()] = handler
+
+    def process(self, command_string: str) -> str:
+        """Process a SCPI command string and return the response.
+
+        Args:
+            command_string: Raw SCPI command string to process.
+
+        Returns:
+            Response string. Empty string for commands with no response.
+            Error string starting with "ERROR:" for invalid commands.
+        """
+        command = self._parser.parse(command_string)
+
+        if not command.header:
+            return ""
+
+        # Look up handler by keyword (without '?' suffix)
+        keyword = command.keyword.upper()
+        handler = self._handlers.get(keyword)
+
+        if handler is None:
+            return f"ERROR: Unknown command '{keyword}'"
+
+        try:
+            return handler(command)
+        except ValueError as e:
+            return f"ERROR: {e}"
+        except Exception as e:
+            return f"ERROR: Internal error - {e}"
+
+    def _handle_idn(self, command: SCPICommand) -> str:
+        """Handle *IDN? identification query.
+
+        Returns:
+            Comma-separated identification string.
+        """
+        if not command.is_query:
+            return "ERROR: *IDN is query only"
+        return f"{self.manufacturer},{self.model},{self.serial_number},{self.firmware_version}"
+
+    def _handle_rst(self, command: SCPICommand) -> str:
+        """Handle *RST reset command.
+
+        Returns:
+            Empty string (no response for reset).
+        """
+        if command.is_query:
+            return "ERROR: *RST is command only"
+        self.reset()
+        return ""
+
+    def _handle_cls(self, command: SCPICommand) -> str:
+        """Handle *CLS clear status command.
+
+        Returns:
+            Empty string (no response for clear).
+        """
+        if command.is_query:
+            return "ERROR: *CLS is command only"
+        return ""
+
+    def _handle_opc(self, command: SCPICommand) -> str:
+        """Handle *OPC operation complete command/query.
+
+        Returns:
+            "1" for query, empty string for command.
+        """
+        if command.is_query:
+            return "1"
+        return ""
+
+    @abstractmethod
+    def reset(self) -> None:
+        """Reset instrument to default state.
+
+        Subclasses must implement this to define reset behaviour.
+        """

src/py_dvt_ate/simulation/virtual/chamber.py

@@ -0,0 +1,143 @@
+"""Virtual thermal chamber simulator.
+
+This module implements a SCPI-based virtual thermal chamber that interfaces
+with the physics engine to provide realistic temperature control simulation.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from py_dvt_ate.instruments.scpi import SCPICommand
+from py_dvt_ate.simulation.virtual.base import BaseInstrument
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+
+
+class ThermalChamberSim(BaseInstrument):
+    """Virtual thermal chamber simulator.
+
+    Simulates a thermal chamber with SCPI control interface. The chamber
+    temperature behaviour is driven by the physics engine.
+
+    SCPI Commands:
+        TEMP:SETPOINT <value>  - Set target temperature in degrees C
+        TEMP:SETPOINT?         - Query current setpoint
+        TEMP:ACTUAL?           - Query actual chamber temperature
+        TEMP:STAB?             - Query temperature stability (1=stable, 0=settling)
+
+    Attributes:
+        manufacturer: "PyDVTATE"
+        model: "TC-SIM-001"
+    """
+
+    manufacturer = "PyDVTATE"
+    model = "TC-SIM-001"
+    serial_number = "TCSIM001"
+    firmware_version = "1.0.0"
+
+    # Stability threshold in degrees C
+    STABILITY_THRESHOLD = 0.5
+
+    def __init__(self, physics_engine: PhysicsEngine | None = None) -> None:
+        """Initialise the thermal chamber simulator.
+
+        Args:
+            physics_engine: Reference to physics engine for temperature state.
+        """
+        self._setpoint = 25.0  # Default setpoint
+        super().__init__(physics_engine)
+
+    def _setup_commands(self) -> None:
+        """Register thermal chamber SCPI commands."""
+        self.register_command("TEMP:SETPOINT", self._handle_temp_setpoint)
+        self.register_command("TEMP:ACTUAL", self._handle_temp_actual)
+        self.register_command("TEMP:STAB", self._handle_temp_stab)
+
+    def reset(self) -> None:
+        """Reset chamber to default state."""
+        self._setpoint = 25.0
+        if self._physics_engine is not None:
+            self._physics_engine.set_chamber_setpoint(self._setpoint)
+
+    def _handle_temp_setpoint(self, command: SCPICommand) -> str:
+        """Handle TEMP:SETPOINT command/query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Setpoint value for query, empty string for set command.
+
+        Raises:
+            ValueError: If setpoint argument is invalid.
+        """
+        if command.is_query:
+            return f"{self._setpoint:.2f}"
+
+        # Set command requires one argument
+        if not command.arguments:
+            raise ValueError("TEMP:SETPOINT requires a value")
+
+        try:
+            setpoint = float(command.arguments[0])
+        except ValueError:
+            raise ValueError(f"Invalid temperature value: {command.arguments[0]}")
+
+        self._setpoint = setpoint
+        if self._physics_engine is not None:
+            self._physics_engine.set_chamber_setpoint(setpoint)
+
+        return ""
+
+    def _handle_temp_actual(self, command: SCPICommand) -> str:
+        """Handle TEMP:ACTUAL? query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Actual chamber temperature.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("TEMP:ACTUAL is query only")
+
+        if self._physics_engine is None:
+            # Return setpoint if no physics engine connected
+            return f"{self._setpoint:.2f}"
+
+        thermal_state = self._physics_engine.get_thermal_state()
+        return f"{thermal_state.chamber_temperature:.2f}"
+
+    def _handle_temp_stab(self, command: SCPICommand) -> str:
+        """Handle TEMP:STAB? stability query.
+
+        Temperature is considered stable when the actual chamber temperature
+        is within STABILITY_THRESHOLD of the setpoint.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            "1" if stable, "0" if settling.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("TEMP:STAB is query only")
+
+        if self._physics_engine is None:
+            # Assume stable if no physics engine connected
+            return "1"
+
+        thermal_state = self._physics_engine.get_thermal_state()
+        error = abs(thermal_state.chamber_temperature - self._setpoint)
+
+        if error <= self.STABILITY_THRESHOLD:
+            return "1"
+        return "0"

src/py_dvt_ate/simulation/virtual/multimeter.py

@@ -0,0 +1,213 @@
+"""Virtual digital multimeter (DMM) simulator.
+
+This module implements a SCPI-based virtual multimeter that interfaces
+with the physics engine to measure DUT electrical parameters.
+"""
+
+from __future__ import annotations
+
+from enum import Enum
+from typing import TYPE_CHECKING
+
+from py_dvt_ate.instruments.scpi import SCPICommand
+from py_dvt_ate.simulation.virtual.base import BaseInstrument
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+
+
+class MeasurementFunction(Enum):
+    """Available measurement functions."""
+
+    VOLTAGE_DC = "VOLT:DC"
+    CURRENT_DC = "CURR:DC"
+
+
+class MultimeterSim(BaseInstrument):
+    """Virtual digital multimeter simulator.
+
+    Simulates a digital multimeter with SCPI control interface. The DMM
+    measures DUT output voltage and load current via the physics engine.
+
+    SCPI Commands:
+        MEAS:VOLT:DC?      - Measure DC voltage (shortcut)
+        MEAS:CURR:DC?      - Measure DC current (shortcut)
+        CONF:VOLT:DC       - Configure for DC voltage measurement
+        CONF:CURR:DC       - Configure for DC current measurement
+        CONF?              - Query current configuration
+        READ?              - Take measurement with current configuration
+
+    Attributes:
+        manufacturer: "PyDVTATE"
+        model: "DMM-SIM-001"
+    """
+
+    manufacturer = "PyDVTATE"
+    model = "DMM-SIM-001"
+    serial_number = "DMMSIM001"
+    firmware_version = "1.0.0"
+
+    def __init__(self, physics_engine: PhysicsEngine | None = None) -> None:
+        """Initialise the multimeter simulator.
+
+        Args:
+            physics_engine: Reference to physics engine for measurement values.
+        """
+        self._function = MeasurementFunction.VOLTAGE_DC
+        super().__init__(physics_engine)
+
+    def _setup_commands(self) -> None:
+        """Register multimeter SCPI commands."""
+        self.register_command("MEAS:VOLT:DC", self._handle_meas_volt_dc)
+        self.register_command("MEAS:CURR:DC", self._handle_meas_curr_dc)
+        self.register_command("CONF:VOLT:DC", self._handle_conf_volt_dc)
+        self.register_command("CONF:CURR:DC", self._handle_conf_curr_dc)
+        self.register_command("CONF", self._handle_conf)
+        self.register_command("READ", self._handle_read)
+
+    def reset(self) -> None:
+        """Reset multimeter to default state."""
+        self._function = MeasurementFunction.VOLTAGE_DC
+
+    def _handle_meas_volt_dc(self, command: SCPICommand) -> str:
+        """Handle MEAS:VOLT:DC? query.
+
+        Configures for DC voltage and takes measurement in one command.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Measured DC voltage.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("MEAS:VOLT:DC is query only")
+
+        self._function = MeasurementFunction.VOLTAGE_DC
+        return self._measure_voltage_dc()
+
+    def _handle_meas_curr_dc(self, command: SCPICommand) -> str:
+        """Handle MEAS:CURR:DC? query.
+
+        Configures for DC current and takes measurement in one command.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Measured DC current.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("MEAS:CURR:DC is query only")
+
+        self._function = MeasurementFunction.CURRENT_DC
+        return self._measure_current_dc()
+
+    def _handle_conf_volt_dc(self, command: SCPICommand) -> str:
+        """Handle CONF:VOLT:DC command.
+
+        Configures multimeter for DC voltage measurement.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Empty string (no response for configuration).
+
+        Raises:
+            ValueError: If used as query.
+        """
+        if command.is_query:
+            raise ValueError("CONF:VOLT:DC is command only")
+
+        self._function = MeasurementFunction.VOLTAGE_DC
+        return ""
+
+    def _handle_conf_curr_dc(self, command: SCPICommand) -> str:
+        """Handle CONF:CURR:DC command.
+
+        Configures multimeter for DC current measurement.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Empty string (no response for configuration).
+
+        Raises:
+            ValueError: If used as query.
+        """
+        if command.is_query:
+            raise ValueError("CONF:CURR:DC is command only")
+
+        self._function = MeasurementFunction.CURRENT_DC
+        return ""
+
+    def _handle_conf(self, command: SCPICommand) -> str:
+        """Handle CONF? query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Current measurement configuration.
+
+        Raises:
+            ValueError: If used as command without subcommand.
+        """
+        if not command.is_query:
+            raise ValueError("CONF requires a function (e.g., CONF:VOLT:DC)")
+
+        return f'"{self._function.value}"'
+
+    def _handle_read(self, command: SCPICommand) -> str:
+        """Handle READ? query.
+
+        Takes measurement using current configuration.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Measured value.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("READ is query only")
+
+        if self._function == MeasurementFunction.VOLTAGE_DC:
+            return self._measure_voltage_dc()
+        else:
+            return self._measure_current_dc()
+
+    def _measure_voltage_dc(self) -> str:
+        """Measure DC voltage from physics engine.
+
+        Returns:
+            Formatted voltage reading.
+        """
+        if self._physics_engine is None:
+            return "0.000000"
+
+        electrical_state = self._physics_engine.get_electrical_state()
+        return f"{electrical_state.output_voltage:.6f}"
+
+    def _measure_current_dc(self) -> str:
+        """Measure DC current from physics engine.
+
+        Returns:
+            Formatted current reading.
+        """
+        if self._physics_engine is None:
+            return "0.000000"
+
+        electrical_state = self._physics_engine.get_electrical_state()
+        return f"{electrical_state.load_current:.6f}"

src/py_dvt_ate/simulation/virtual/power_supply.py

@@ -0,0 +1,222 @@
+"""Virtual power supply simulator.
+
+This module implements a SCPI-based virtual power supply that interfaces
+with the physics engine to provide realistic power supply simulation.
+"""
+
+from __future__ import annotations
+
+from typing import TYPE_CHECKING
+
+from py_dvt_ate.instruments.scpi import SCPICommand
+from py_dvt_ate.simulation.virtual.base import BaseInstrument
+
+if TYPE_CHECKING:
+    from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+
+
+class PowerSupplySim(BaseInstrument):
+    """Virtual power supply simulator.
+
+    Simulates a programmable DC power supply with SCPI control interface.
+    The power supply provides input voltage to the DUT via the physics engine.
+
+    SCPI Commands:
+        VOLT <value>       - Set output voltage in volts
+        VOLT?              - Query voltage setpoint
+        CURR <value>       - Set current limit in amps
+        CURR?              - Query current limit
+        OUTP <ON|OFF|1|0>  - Enable/disable output
+        OUTP?              - Query output state (1=on, 0=off)
+        MEAS:VOLT?         - Measure actual output voltage
+        MEAS:CURR?         - Measure actual output current
+
+    Attributes:
+        manufacturer: "PyDVTATE"
+        model: "PS-SIM-001"
+    """
+
+    manufacturer = "PyDVTATE"
+    model = "PS-SIM-001"
+    serial_number = "PSSIM001"
+    firmware_version = "1.0.0"
+
+    # Default values
+    DEFAULT_VOLTAGE = 0.0
+    DEFAULT_CURRENT_LIMIT = 1.0
+
+    def __init__(self, physics_engine: PhysicsEngine | None = None) -> None:
+        """Initialise the power supply simulator.
+
+        Args:
+            physics_engine: Reference to physics engine for electrical state.
+        """
+        self._voltage_setpoint = self.DEFAULT_VOLTAGE
+        self._current_limit = self.DEFAULT_CURRENT_LIMIT
+        self._output_enabled = False
+        super().__init__(physics_engine)
+
+    def _setup_commands(self) -> None:
+        """Register power supply SCPI commands."""
+        self.register_command("VOLT", self._handle_volt)
+        self.register_command("CURR", self._handle_curr)
+        self.register_command("OUTP", self._handle_outp)
+        self.register_command("MEAS:VOLT", self._handle_meas_volt)
+        self.register_command("MEAS:CURR", self._handle_meas_curr)
+
+    def reset(self) -> None:
+        """Reset power supply to default state."""
+        self._voltage_setpoint = self.DEFAULT_VOLTAGE
+        self._current_limit = self.DEFAULT_CURRENT_LIMIT
+        self._output_enabled = False
+
+        if self._physics_engine is not None:
+            self._physics_engine.set_input_voltage(0.0)
+            self._physics_engine.set_output_enabled(False)
+
+    def _handle_volt(self, command: SCPICommand) -> str:
+        """Handle VOLT command/query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Voltage setpoint for query, empty string for set command.
+
+        Raises:
+            ValueError: If voltage argument is invalid.
+        """
+        if command.is_query:
+            return f"{self._voltage_setpoint:.3f}"
+
+        if not command.arguments:
+            raise ValueError("VOLT requires a value")
+
+        try:
+            voltage = float(command.arguments[0])
+        except ValueError:
+            raise ValueError(f"Invalid voltage value: {command.arguments[0]}")
+
+        if voltage < 0:
+            raise ValueError("Voltage cannot be negative")
+
+        self._voltage_setpoint = voltage
+
+        if self._physics_engine is not None and self._output_enabled:
+            self._physics_engine.set_input_voltage(voltage)
+
+        return ""
+
+    def _handle_curr(self, command: SCPICommand) -> str:
+        """Handle CURR command/query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Current limit for query, empty string for set command.
+
+        Raises:
+            ValueError: If current argument is invalid.
+        """
+        if command.is_query:
+            return f"{self._current_limit:.3f}"
+
+        if not command.arguments:
+            raise ValueError("CURR requires a value")
+
+        try:
+            current = float(command.arguments[0])
+        except ValueError:
+            raise ValueError(f"Invalid current value: {command.arguments[0]}")
+
+        if current < 0:
+            raise ValueError("Current limit cannot be negative")
+
+        self._current_limit = current
+        return ""
+
+    def _handle_outp(self, command: SCPICommand) -> str:
+        """Handle OUTP command/query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            "1" or "0" for query, empty string for set command.
+
+        Raises:
+            ValueError: If output argument is invalid.
+        """
+        if command.is_query:
+            return "1" if self._output_enabled else "0"
+
+        if not command.arguments:
+            raise ValueError("OUTP requires a value (ON, OFF, 1, or 0)")
+
+        arg = command.arguments[0].upper()
+        if arg in ("ON", "1"):
+            self._output_enabled = True
+        elif arg in ("OFF", "0"):
+            self._output_enabled = False
+        else:
+            raise ValueError(f"Invalid output state: {command.arguments[0]}")
+
+        if self._physics_engine is not None:
+            self._physics_engine.set_output_enabled(self._output_enabled)
+            if self._output_enabled:
+                self._physics_engine.set_input_voltage(self._voltage_setpoint)
+            else:
+                self._physics_engine.set_input_voltage(0.0)
+
+        return ""
+
+    def _handle_meas_volt(self, command: SCPICommand) -> str:
+        """Handle MEAS:VOLT? query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Measured output voltage.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("MEAS:VOLT is query only")
+
+        if not self._output_enabled:
+            return "0.000"
+
+        if self._physics_engine is None:
+            return f"{self._voltage_setpoint:.3f}"
+
+        electrical_state = self._physics_engine.get_electrical_state()
+        return f"{electrical_state.input_voltage:.3f}"
+
+    def _handle_meas_curr(self, command: SCPICommand) -> str:
+        """Handle MEAS:CURR? query.
+
+        Args:
+            command: Parsed SCPI command.
+
+        Returns:
+            Measured output current.
+
+        Raises:
+            ValueError: If used as command (not query).
+        """
+        if not command.is_query:
+            raise ValueError("MEAS:CURR is query only")
+
+        if not self._output_enabled:
+            return "0.000"
+
+        if self._physics_engine is None:
+            return "0.000"
+
+        electrical_state = self._physics_engine.get_electrical_state()
+        # Total current is load current + quiescent current
+        total_current = electrical_state.load_current + electrical_state.quiescent_current
+        return f"{total_current:.3f}"

src/py_dvt_ate/tests/__init__.py

@@ -1 +1,6 @@
-"""DVT test implementations."""
+"""DVT test implementations.
+
+Contains characterisation test suites organised by category:
+- thermal/ - Temperature-related tests (TempCo, etc.)
+- electrical/ - Electrical tests (load regulation, etc.)
+"""

src/py_dvt_ate/tests/electrical/__init__.py

@@ -0,0 +1,5 @@
+"""Electrical characterisation tests.
+
+Tests for electrical performance including load regulation,
+line regulation, and output accuracy.
+"""

src/py_dvt_ate/tests/thermal/__init__.py

@@ -0,0 +1,5 @@
+"""Thermal characterisation tests.
+
+Tests related to temperature behaviour including temperature
+coefficient (TempCo) measurements and thermal stability.
+"""

src/py_dvt_ate/transport/__init__.py

@@ -1 +0,0 @@
-"""Communication layer."""

tests/conftest.py

@@ -1 +1,8 @@
 """pytest fixtures for py_dvt_ate tests."""
+
+import pytest
+
+
+def pytest_configure(config: pytest.Config) -> None:
+    """Configure pytest markers."""
+    config.addinivalue_line("markers", "asyncio: mark test as async")

tests/integration/__init__.py

@@ -0,0 +1 @@
+"""Integration tests for py_dvt_ate."""

tests/integration/conftest.py

@@ -0,0 +1 @@
+"""Configuration for integration tests."""

tests/integration/test_tcp_server.py

@@ -0,0 +1,274 @@
+"""Integration tests for TCP server.
+
+Tests the InstrumentServer and SimulationServer with actual TCP connections.
+"""
+
+from __future__ import annotations
+
+import asyncio
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.server import ServerConfig, SimulationServer
+from py_dvt_ate.simulation.tcp_server import InstrumentServer
+from py_dvt_ate.simulation.virtual.chamber import ThermalChamberSim
+from py_dvt_ate.simulation.virtual.multimeter import MultimeterSim
+from py_dvt_ate.simulation.virtual.power_supply import PowerSupplySim
+
+
+@pytest.mark.asyncio(loop_scope="function")
+class TestInstrumentServer:
+    """Tests for InstrumentServer TCP functionality."""
+
+    @pytest.fixture
+    def physics_engine(self) -> PhysicsEngine:
+        """Create a physics engine for testing."""
+        return PhysicsEngine(update_rate_hz=100.0)
+
+    @pytest.fixture
+    def server(self, physics_engine: PhysicsEngine) -> InstrumentServer:
+        """Create an instrument server with a thermal chamber."""
+        server = InstrumentServer(host="127.0.0.1")
+        chamber = ThermalChamberSim(physics_engine)
+        server.register_instrument(15000, chamber)
+        return server
+
+    async def test_server_start_stop(self, server: InstrumentServer) -> None:
+        """Test server can start and stop."""
+        assert not server.is_running
+
+        await server.start()
+        assert server.is_running
+
+        await server.stop()
+        assert not server.is_running
+
+    async def test_client_connection(self, server: InstrumentServer) -> None:
+        """Test client can connect and send command."""
+        await server.start()
+
+        try:
+            reader, writer = await asyncio.open_connection("127.0.0.1", 15000)
+
+            # Send *IDN? query
+            writer.write(b"*IDN?\n")
+            await writer.drain()
+
+            # Read response
+            response = await asyncio.wait_for(reader.readline(), timeout=2.0)
+            assert b"PyDVTATE" in response
+            assert b"TC-SIM-001" in response
+
+            writer.close()
+            await writer.wait_closed()
+        finally:
+            await server.stop()
+
+    async def test_multiple_commands(self, server: InstrumentServer) -> None:
+        """Test sending multiple commands in sequence."""
+        await server.start()
+
+        try:
+            reader, writer = await asyncio.open_connection("127.0.0.1", 15000)
+
+            # Set temperature setpoint
+            writer.write(b"TEMP:SETPOINT 85.0\n")
+            await writer.drain()
+
+            # Query setpoint
+            writer.write(b"TEMP:SETPOINT?\n")
+            await writer.drain()
+            response = await asyncio.wait_for(reader.readline(), timeout=2.0)
+            assert b"85.00" in response
+
+            # Query actual temperature
+            writer.write(b"TEMP:ACTUAL?\n")
+            await writer.drain()
+            response = await asyncio.wait_for(reader.readline(), timeout=2.0)
+            # Should return a valid float
+            temp = float(response.decode().strip())
+            assert -50 <= temp <= 200
+
+            writer.close()
+            await writer.wait_closed()
+        finally:
+            await server.stop()
+
+    async def test_concurrent_connections(
+        self, physics_engine: PhysicsEngine
+    ) -> None:
+        """Test multiple concurrent client connections."""
+        server = InstrumentServer(host="127.0.0.1")
+        chamber = ThermalChamberSim(physics_engine)
+        server.register_instrument(15001, chamber)
+
+        await server.start()
+
+        try:
+            # Connect two clients simultaneously
+            reader1, writer1 = await asyncio.open_connection("127.0.0.1", 15001)
+            reader2, writer2 = await asyncio.open_connection("127.0.0.1", 15001)
+
+            # Send command from client 1
+            writer1.write(b"*IDN?\n")
+            await writer1.drain()
+            response1 = await asyncio.wait_for(reader1.readline(), timeout=2.0)
+
+            # Send command from client 2
+            writer2.write(b"*IDN?\n")
+            await writer2.drain()
+            response2 = await asyncio.wait_for(reader2.readline(), timeout=2.0)
+
+            # Both should get valid responses
+            assert b"TC-SIM-001" in response1
+            assert b"TC-SIM-001" in response2
+
+            writer1.close()
+            writer2.close()
+            await writer1.wait_closed()
+            await writer2.wait_closed()
+        finally:
+            await server.stop()
+
+
+@pytest.mark.asyncio(loop_scope="function")
+class TestSimulationServer:
+    """Tests for complete SimulationServer."""
+
+    async def test_simulation_server_start_stop(self) -> None:
+        """Test simulation server lifecycle."""
+        config = ServerConfig(
+            host="127.0.0.1",
+            chamber_port=16000,
+            psu_port=16001,
+            dmm_port=16002,
+            physics_rate_hz=100.0,
+        )
+        server = SimulationServer(config)
+
+        assert not server.is_running
+
+        await server.start()
+        assert server.is_running
+        assert server.physics_engine is not None
+
+        await server.stop()
+        assert not server.is_running
+
+    async def test_all_instruments_accessible(self) -> None:
+        """Test all three instruments are accessible over TCP."""
+        config = ServerConfig(
+            host="127.0.0.1",
+            chamber_port=16100,
+            psu_port=16101,
+            dmm_port=16102,
+        )
+        server = SimulationServer(config)
+        await server.start()
+
+        try:
+            # Test thermal chamber
+            r, w = await asyncio.open_connection("127.0.0.1", 16100)
+            w.write(b"*IDN?\n")
+            await w.drain()
+            resp = await asyncio.wait_for(r.readline(), timeout=2.0)
+            assert b"TC-SIM-001" in resp
+            w.close()
+            await w.wait_closed()
+
+            # Test power supply
+            r, w = await asyncio.open_connection("127.0.0.1", 16101)
+            w.write(b"*IDN?\n")
+            await w.drain()
+            resp = await asyncio.wait_for(r.readline(), timeout=2.0)
+            assert b"PS-SIM-001" in resp
+            w.close()
+            await w.wait_closed()
+
+            # Test multimeter
+            r, w = await asyncio.open_connection("127.0.0.1", 16102)
+            w.write(b"*IDN?\n")
+            await w.drain()
+            resp = await asyncio.wait_for(r.readline(), timeout=2.0)
+            assert b"DMM-SIM-001" in resp
+            w.close()
+            await w.wait_closed()
+
+        finally:
+            await server.stop()
+
+    async def test_physics_engine_integration(self) -> None:
+        """Test instruments share physics engine state."""
+        config = ServerConfig(
+            host="127.0.0.1",
+            chamber_port=16200,
+            psu_port=16201,
+            dmm_port=16202,
+        )
+        server = SimulationServer(config)
+        await server.start()
+
+        try:
+            # Connect to power supply and enable output
+            psu_r, psu_w = await asyncio.open_connection("127.0.0.1", 16201)
+            psu_w.write(b"VOLT 5.0\n")
+            await psu_w.drain()
+            psu_w.write(b"OUTP ON\n")
+            await psu_w.drain()
+
+            # Run a few physics steps
+            await asyncio.sleep(0.1)
+
+            # Query voltage from power supply
+            psu_w.write(b"MEAS:VOLT?\n")
+            await psu_w.drain()
+            psu_resp = await asyncio.wait_for(psu_r.readline(), timeout=2.0)
+            psu_voltage = float(psu_resp.decode().strip())
+
+            # Connect to DMM and measure DUT output
+            dmm_r, dmm_w = await asyncio.open_connection("127.0.0.1", 16202)
+            dmm_w.write(b"MEAS:VOLT:DC?\n")
+            await dmm_w.drain()
+            dmm_resp = await asyncio.wait_for(dmm_r.readline(), timeout=2.0)
+            dmm_voltage = float(dmm_resp.decode().strip())
+
+            # PSU should show input voltage (5V)
+            assert 4.9 <= psu_voltage <= 5.1
+
+            # DMM should show DUT output voltage (LDO regulated ~3.3V)
+            assert 3.0 <= dmm_voltage <= 3.5
+
+            psu_w.close()
+            dmm_w.close()
+            await psu_w.wait_closed()
+            await dmm_w.wait_closed()
+
+        finally:
+            await server.stop()
+
+    async def test_error_handling(self) -> None:
+        """Test invalid commands return errors."""
+        config = ServerConfig(
+            host="127.0.0.1",
+            chamber_port=16300,
+            psu_port=16301,
+            dmm_port=16302,
+        )
+        server = SimulationServer(config)
+        await server.start()
+
+        try:
+            r, w = await asyncio.open_connection("127.0.0.1", 16300)
+
+            # Send invalid command
+            w.write(b"INVALID:COMMAND\n")
+            await w.drain()
+            resp = await asyncio.wait_for(r.readline(), timeout=2.0)
+            assert b"ERROR" in resp
+
+            w.close()
+            await w.wait_closed()
+
+        finally:
+            await server.stop()

tests/unit/test_multimeter.py

@@ -0,0 +1,306 @@
+"""Unit tests for multimeter simulator."""
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.virtual.multimeter import MultimeterSim
+
+
+class TestMultimeterSimBasic:
+    """Tests for MultimeterSim without physics engine."""
+
+    @pytest.fixture
+    def dmm(self) -> MultimeterSim:
+        """Create multimeter instance without physics engine."""
+        return MultimeterSim()
+
+    def test_creation(self, dmm: MultimeterSim) -> None:
+        """Test multimeter can be created."""
+        assert dmm is not None
+        assert dmm.model == "DMM-SIM-001"
+        assert dmm.manufacturer == "PyDVTATE"
+
+    def test_idn_query(self, dmm: MultimeterSim) -> None:
+        """Test *IDN? returns identification string."""
+        response = dmm.process("*IDN?")
+
+        assert "PyDVTATE" in response
+        assert "DMM-SIM-001" in response
+
+    def test_rst_command(self, dmm: MultimeterSim) -> None:
+        """Test *RST resets to defaults."""
+        # Set non-default config
+        dmm.process("CONF:CURR:DC")
+        assert dmm.process("CONF?") == '"CURR:DC"'
+
+        # Reset
+        response = dmm.process("*RST")
+        assert response == ""
+
+        # Check defaults restored
+        assert dmm.process("CONF?") == '"VOLT:DC"'
+
+    def test_opc_query(self, dmm: MultimeterSim) -> None:
+        """Test *OPC? returns 1."""
+        response = dmm.process("*OPC?")
+        assert response == "1"
+
+    def test_unknown_command(self, dmm: MultimeterSim) -> None:
+        """Test unknown command returns error."""
+        response = dmm.process("INVALID:CMD")
+
+        assert response.startswith("ERROR:")
+        assert "Unknown command" in response
+
+
+class TestMultimeterMeasVoltDC:
+    """Tests for MEAS:VOLT:DC command."""
+
+    @pytest.fixture
+    def dmm(self) -> MultimeterSim:
+        """Create multimeter instance without physics engine."""
+        return MultimeterSim()
+
+    def test_meas_volt_dc_query_no_engine(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:VOLT:DC? returns 0 without physics engine."""
+        response = dmm.process("MEAS:VOLT:DC?")
+
+        assert response == "0.000000"
+
+    def test_meas_volt_dc_sets_config(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:VOLT:DC? sets configuration to VOLT:DC."""
+        dmm.process("CONF:CURR:DC")
+        dmm.process("MEAS:VOLT:DC?")
+
+        assert dmm.process("CONF?") == '"VOLT:DC"'
+
+    def test_meas_volt_dc_as_command_fails(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:VOLT:DC (without ?) returns error."""
+        response = dmm.process("MEAS:VOLT:DC 1.0")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestMultimeterMeasCurrDC:
+    """Tests for MEAS:CURR:DC command."""
+
+    @pytest.fixture
+    def dmm(self) -> MultimeterSim:
+        """Create multimeter instance without physics engine."""
+        return MultimeterSim()
+
+    def test_meas_curr_dc_query_no_engine(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:CURR:DC? returns 0 without physics engine."""
+        response = dmm.process("MEAS:CURR:DC?")
+
+        assert response == "0.000000"
+
+    def test_meas_curr_dc_sets_config(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:CURR:DC? sets configuration to CURR:DC."""
+        dmm.process("MEAS:CURR:DC?")
+
+        assert dmm.process("CONF?") == '"CURR:DC"'
+
+    def test_meas_curr_dc_as_command_fails(self, dmm: MultimeterSim) -> None:
+        """Test MEAS:CURR:DC (without ?) returns error."""
+        response = dmm.process("MEAS:CURR:DC 0.1")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestMultimeterConf:
+    """Tests for CONF commands."""
+
+    @pytest.fixture
+    def dmm(self) -> MultimeterSim:
+        """Create multimeter instance without physics engine."""
+        return MultimeterSim()
+
+    def test_conf_query_default(self, dmm: MultimeterSim) -> None:
+        """Test CONF? returns default configuration."""
+        response = dmm.process("CONF?")
+
+        assert response == '"VOLT:DC"'
+
+    def test_conf_volt_dc(self, dmm: MultimeterSim) -> None:
+        """Test CONF:VOLT:DC sets voltage measurement mode."""
+        dmm.process("CONF:CURR:DC")
+        response = dmm.process("CONF:VOLT:DC")
+
+        assert response == ""
+        assert dmm.process("CONF?") == '"VOLT:DC"'
+
+    def test_conf_volt_dc_as_query_fails(self, dmm: MultimeterSim) -> None:
+        """Test CONF:VOLT:DC? returns error."""
+        response = dmm.process("CONF:VOLT:DC?")
+
+        assert response.startswith("ERROR:")
+        assert "command only" in response
+
+    def test_conf_curr_dc(self, dmm: MultimeterSim) -> None:
+        """Test CONF:CURR:DC sets current measurement mode."""
+        response = dmm.process("CONF:CURR:DC")
+
+        assert response == ""
+        assert dmm.process("CONF?") == '"CURR:DC"'
+
+    def test_conf_curr_dc_as_query_fails(self, dmm: MultimeterSim) -> None:
+        """Test CONF:CURR:DC? returns error."""
+        response = dmm.process("CONF:CURR:DC?")
+
+        assert response.startswith("ERROR:")
+        assert "command only" in response
+
+    def test_conf_as_command_fails(self, dmm: MultimeterSim) -> None:
+        """Test CONF without subcommand returns error."""
+        response = dmm.process("CONF")
+
+        assert response.startswith("ERROR:")
+
+
+class TestMultimeterRead:
+    """Tests for READ command."""
+
+    @pytest.fixture
+    def dmm(self) -> MultimeterSim:
+        """Create multimeter instance without physics engine."""
+        return MultimeterSim()
+
+    def test_read_query_volt_mode(self, dmm: MultimeterSim) -> None:
+        """Test READ? returns voltage when configured for voltage."""
+        dmm.process("CONF:VOLT:DC")
+        response = dmm.process("READ?")
+
+        assert response == "0.000000"
+
+    def test_read_query_curr_mode(self, dmm: MultimeterSim) -> None:
+        """Test READ? returns current when configured for current."""
+        dmm.process("CONF:CURR:DC")
+        response = dmm.process("READ?")
+
+        assert response == "0.000000"
+
+    def test_read_as_command_fails(self, dmm: MultimeterSim) -> None:
+        """Test READ (without ?) returns error."""
+        response = dmm.process("READ")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestMultimeterWithPhysicsEngine:
+    """Tests for MultimeterSim with physics engine integration."""
+
+    @pytest.fixture
+    def engine(self) -> PhysicsEngine:
+        """Create physics engine instance."""
+        return PhysicsEngine(update_rate_hz=100.0)
+
+    @pytest.fixture
+    def dmm(self, engine: PhysicsEngine) -> MultimeterSim:
+        """Create multimeter instance with physics engine."""
+        return MultimeterSim(physics_engine=engine)
+
+    def test_meas_volt_dc_returns_engine_voltage(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:VOLT:DC? returns physics engine output voltage."""
+        engine.set_input_voltage(5.0)
+        engine.set_output_enabled(True)
+        engine.step()
+
+        response = dmm.process("MEAS:VOLT:DC?")
+
+        # LDO model outputs ~3.3V nominal
+        voltage = float(response)
+        assert voltage > 3.0
+        assert voltage < 4.0
+
+    def test_meas_volt_dc_returns_zero_when_disabled(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:VOLT:DC? returns 0 when DUT output disabled."""
+        engine.set_input_voltage(5.0)
+        engine.set_output_enabled(False)
+        engine.step()
+
+        response = dmm.process("MEAS:VOLT:DC?")
+
+        assert response == "0.000000"
+
+    def test_meas_curr_dc_returns_engine_current(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:CURR:DC? returns physics engine load current."""
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.1)
+        engine.set_output_enabled(True)
+        engine.step()
+
+        response = dmm.process("MEAS:CURR:DC?")
+
+        assert float(response) == pytest.approx(0.1, abs=0.001)
+
+    def test_meas_curr_dc_returns_zero_when_disabled(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:CURR:DC? returns 0 when DUT output disabled."""
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.1)
+        engine.set_output_enabled(False)
+        engine.step()
+
+        response = dmm.process("MEAS:CURR:DC?")
+
+        assert response == "0.000000"
+
+    def test_read_uses_configured_function(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test READ? respects configured measurement function."""
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.1)
+        engine.set_output_enabled(True)
+        engine.step()
+
+        # Configure for current
+        dmm.process("CONF:CURR:DC")
+        response = dmm.process("READ?")
+
+        # Should return current, not voltage
+        assert float(response) == pytest.approx(0.1, abs=0.001)
+
+    def test_reset_restores_voltage_mode(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test *RST restores default voltage measurement mode."""
+        dmm.process("CONF:CURR:DC")
+        dmm.process("*RST")
+
+        assert dmm.process("CONF?") == '"VOLT:DC"'
+
+    def test_voltage_changes_with_temperature(
+        self, dmm: MultimeterSim, engine: PhysicsEngine
+    ) -> None:
+        """Test measured voltage changes with DUT temperature."""
+        engine.set_input_voltage(5.0)
+        engine.set_output_enabled(True)
+        engine.step()
+
+        # Measure at initial temperature
+        response1 = dmm.process("MEAS:VOLT:DC?")
+        v1 = float(response1)
+
+        # Change chamber temperature and let settle
+        engine.set_chamber_setpoint(85.0)
+        for _ in range(5000):  # Let temperature settle somewhat
+            engine.step()
+
+        # Measure at elevated temperature
+        response2 = dmm.process("MEAS:VOLT:DC?")
+        v2 = float(response2)
+
+        # Output voltage should have changed (LDO has tempco)
+        assert v1 != v2

tests/unit/test_physics_engine.py

@@ -0,0 +1,300 @@
+"""Integration tests for the physics engine with thermal-electrical coupling.
+
+Tests the complete physics simulation including:
+- Thermal settling behaviour (chamber, case, junction)
+- Self-heating effects from power dissipation
+- Temperature-dependent electrical behaviour
+"""
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.physics.models.ldo import LDOModel, LDOParameters
+
+
+class TestThermalSettling:
+    """Tests for thermal settling behaviour."""
+
+    def test_chamber_approaches_setpoint(self) -> None:
+        """Test chamber temperature approaches setpoint over time."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Set a new setpoint
+        engine.set_chamber_setpoint(85.0)
+
+        # Initial state
+        initial_state = engine.get_thermal_state()
+        assert initial_state.chamber_temperature == pytest.approx(25.0)
+
+        # Simulate for 1 second (100 steps at 100Hz)
+        for _ in range(100):
+            engine.step()
+
+        state_1s = engine.get_thermal_state()
+
+        # Chamber should have moved towards 85°C but not reached it yet
+        # With tau=30s, after 1s: T = 25 + (85-25)*(1 - e^(-1/30)) ≈ 27.0°C
+        assert state_1s.chamber_temperature > 25.0
+        assert state_1s.chamber_temperature < 85.0
+
+        # Simulate for another 89 seconds (total 90s = 3*tau)
+        for _ in range(8900):
+            engine.step()
+
+        state_90s = engine.get_thermal_state()
+
+        # After 3 time constants, should be ~95% of the way there
+        # T = 25 + (85-25)*(1 - e^(-3)) ≈ 82.0°C
+        assert state_90s.chamber_temperature > 80.0
+        assert state_90s.chamber_temperature < 85.0
+
+    def test_case_follows_chamber(self) -> None:
+        """Test case temperature follows chamber temperature."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Set chamber to high temperature (no power, so no self-heating)
+        engine.set_chamber_setpoint(85.0)
+
+        # Simulate for 200 seconds (well past both time constants)
+        for _ in range(20000):
+            engine.step()
+
+        state = engine.get_thermal_state()
+
+        # With no power, case should approach chamber temperature
+        assert state.case_temperature == pytest.approx(
+            state.chamber_temperature, abs=0.5
+        )
+
+    def test_junction_equals_case_with_no_power(self) -> None:
+        """Test junction equals case temperature when no power dissipated."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # No power applied (output disabled by default)
+        state = engine.get_thermal_state()
+
+        # Junction should equal case (no θ_jc rise with zero power)
+        assert state.junction_temperature == pytest.approx(state.case_temperature)
+
+
+class TestSelfHeating:
+    """Tests for self-heating effects from power dissipation."""
+
+    def test_junction_higher_than_case_with_power(self) -> None:
+        """Test junction temperature rises above case when power is dissipated."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Apply power: 5V input, 100mA load
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.1)
+        engine.set_output_enabled(True)
+
+        # Let it settle
+        for _ in range(1000):
+            engine.step()
+
+        thermal_state = engine.get_thermal_state()
+        electrical_state = engine.get_electrical_state()
+
+        # Power dissipation = (Vin - Vout) * Iload + Vin * Iq
+        # With Vout ≈ 3.3V, P ≈ (5-3.3)*0.1 ≈ 0.17W
+        assert electrical_state.power_dissipation > 0
+
+        # Junction should be higher than case by P * θ_jc
+        # θ_jc = 15°C/W, so with 0.17W, ΔT ≈ 2.5°C
+        assert (
+            thermal_state.junction_temperature > thermal_state.case_temperature
+        )
+
+    def test_self_heating_raises_case_temperature(self) -> None:
+        """Test self-heating raises case temperature above ambient."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Apply significant power: 5V input, 300mA load
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.3)
+        engine.set_output_enabled(True)
+
+        # Let thermal state settle (many time constants)
+        for _ in range(50000):  # 500 seconds at 100Hz
+            engine.step()
+
+        thermal_state = engine.get_thermal_state()
+
+        # Power ≈ (5-3.3)*0.3 ≈ 0.51W
+        # Steady-state case rise = P * θ_ca = 0.51 * 5 ≈ 2.5°C
+        # Case should be above chamber temperature
+        assert (
+            thermal_state.case_temperature > thermal_state.chamber_temperature
+        )
+
+    def test_self_heating_increases_with_load(self) -> None:
+        """Test that self-heating increases with higher load current."""
+        engine1 = PhysicsEngine(update_rate_hz=100.0)
+        engine2 = PhysicsEngine(update_rate_hz=100.0)
+
+        # Both at 5V, but different loads
+        for engine, load in [(engine1, 0.1), (engine2, 0.3)]:
+            engine.set_input_voltage(5.0)
+            engine.set_load_current(load)
+            engine.set_output_enabled(True)
+
+            # Let settle
+            for _ in range(50000):
+                engine.step()
+
+        state1 = engine1.get_thermal_state()
+        state2 = engine2.get_thermal_state()
+
+        # Higher load should give higher junction temperature
+        assert (
+            state2.junction_temperature > state1.junction_temperature
+        )
+
+
+class TestTemperatureDependentElectrical:
+    """Tests for temperature-dependent electrical behaviour."""
+
+    def test_output_voltage_varies_with_temperature(self) -> None:
+        """Test output voltage changes with junction temperature."""
+        # Create custom LDO with higher tempco for observable effect
+        params = LDOParameters(
+            nominal_output_voltage=3.3,
+            tempco_ppm_per_c=100.0,  # 100 ppm/°C for visible effect
+        )
+        ldo = LDOModel(params=params)
+
+        # Test at different temperatures
+        vout_25 = ldo.calculate_output_voltage(25.0)
+        vout_85 = ldo.calculate_output_voltage(85.0)
+
+        # At 85°C with 100 ppm/°C:
+        # ΔV = 3.3 * 100e-6 * 60 = 19.8mV
+        delta_v = vout_85 - vout_25
+        expected_delta = 3.3 * 100e-6 * 60
+
+        assert delta_v == pytest.approx(expected_delta, rel=0.01)
+
+    def test_quiescent_current_varies_with_temperature(self) -> None:
+        """Test quiescent current changes with junction temperature."""
+        ldo = LDOModel()
+
+        # Test at different temperatures
+        iq_25 = ldo.calculate_quiescent_current(25.0)
+        iq_85 = ldo.calculate_quiescent_current(85.0)
+
+        # Default tempco is 0.003/°C (0.3%/°C)
+        # At 85°C: Iq = Iq_25 * (1 + 0.003 * 60) = Iq_25 * 1.18
+        expected_ratio = 1.0 + 0.003 * 60
+
+        assert iq_85 / iq_25 == pytest.approx(expected_ratio, rel=0.01)
+
+    def test_power_dissipation_calculation(self) -> None:
+        """Test power dissipation is calculated correctly."""
+        ldo = LDOModel()
+        ldo.input_voltage = 5.0
+
+        # P = (Vin - Vout) * Iload + Vin * Iq
+        # At 25°C: Vout ≈ 3.3V, Iq ≈ 50µA
+        # With 100mA load: P ≈ (5-3.3)*0.1 + 5*50e-6 ≈ 0.170W
+        p_diss = ldo.calculate_power_dissipation(
+            input_voltage=5.0,
+            load_current=0.1,
+            junction_temperature=25.0,
+        )
+
+        expected_p = (5.0 - 3.3) * 0.1 + 5.0 * 50e-6
+        assert p_diss == pytest.approx(expected_p, rel=0.01)
+
+
+class TestPhysicsEngineCoupling:
+    """Tests for complete thermal-electrical coupling in the engine."""
+
+    def test_thermal_electrical_feedback(self) -> None:
+        """Test that thermal and electrical states are coupled.
+
+        Higher junction temperature affects Vout, which affects power
+        dissipation, which affects junction temperature - a feedback loop.
+        """
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Apply power at hot chamber
+        engine.set_chamber_setpoint(85.0)
+        engine.set_input_voltage(5.0)
+        engine.set_load_current(0.2)
+        engine.set_output_enabled(True)
+
+        # Let settle completely
+        for _ in range(100000):  # 1000 seconds
+            engine.step()
+
+        thermal = engine.get_thermal_state()
+        electrical = engine.get_electrical_state()
+
+        # Verify the coupling:
+        # 1. Chamber should be near 85°C
+        assert thermal.chamber_temperature == pytest.approx(85.0, abs=0.5)
+
+        # 2. Case should be higher than chamber due to self-heating
+        assert thermal.case_temperature > thermal.chamber_temperature
+
+        # 3. Junction should be higher than case
+        assert thermal.junction_temperature > thermal.case_temperature
+
+        # 4. Output voltage should reflect temperature-adjusted value
+        assert electrical.output_voltage > 0
+        assert electrical.output_voltage < 5.0  # Less than input
+
+        # 5. Power should be non-zero
+        assert electrical.power_dissipation > 0
+
+    def test_engine_with_custom_dut_model(self) -> None:
+        """Test engine works with custom DUT model parameters."""
+        params = LDOParameters(
+            nominal_output_voltage=1.8,  # Different voltage
+            tempco_ppm_per_c=25.0,
+        )
+        ldo = LDOModel(params=params)
+        engine = PhysicsEngine(update_rate_hz=100.0, dut_model=ldo)
+
+        engine.set_input_voltage(3.3)
+        engine.set_load_current(0.1)
+        engine.set_output_enabled(True)
+
+        for _ in range(1000):
+            engine.step()
+
+        electrical = engine.get_electrical_state()
+
+        # Should output approximately 1.8V
+        assert electrical.output_voltage == pytest.approx(1.8, abs=0.01)
+
+    def test_simulation_time_accuracy(self) -> None:
+        """Test simulation time accumulates correctly."""
+        engine = PhysicsEngine(update_rate_hz=1000.0)  # 1ms timestep
+
+        for _ in range(1000):
+            engine.step()
+
+        # Should be exactly 1 second
+        assert engine.simulation_time == pytest.approx(1.0, abs=1e-6)
+
+    def test_multiple_setpoint_changes(self) -> None:
+        """Test engine handles multiple setpoint changes correctly."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        # Start at 25°C, go to 85°C
+        engine.set_chamber_setpoint(85.0)
+        for _ in range(10000):  # 100 seconds
+            engine.step()
+
+        hot_state = engine.get_thermal_state()
+        assert hot_state.chamber_temperature > 75.0
+
+        # Now cool down to -40°C
+        engine.set_chamber_setpoint(-40.0)
+        for _ in range(20000):  # 200 seconds
+            engine.step()
+
+        cold_state = engine.get_thermal_state()
+        assert cold_state.chamber_temperature < -30.0

tests/unit/test_physics_models.py

@@ -0,0 +1,214 @@
+"""Unit tests for physics state dataclasses and engine stub."""
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.physics.state import ElectricalState, ThermalState
+
+
+class TestThermalState:
+    """Tests for the ThermalState dataclass."""
+
+    def test_creation(self) -> None:
+        """Test ThermalState can be created with valid values."""
+        state = ThermalState(
+            chamber_temperature=25.0,
+            case_temperature=30.0,
+            junction_temperature=35.0,
+            timestamp=0.0,
+        )
+
+        assert state.chamber_temperature == 25.0
+        assert state.case_temperature == 30.0
+        assert state.junction_temperature == 35.0
+        assert state.timestamp == 0.0
+
+    def test_immutability(self) -> None:
+        """Test ThermalState is immutable (frozen dataclass)."""
+        state = ThermalState(
+            chamber_temperature=25.0,
+            case_temperature=30.0,
+            junction_temperature=35.0,
+            timestamp=0.0,
+        )
+
+        with pytest.raises(AttributeError):
+            state.chamber_temperature = 50.0  # type: ignore[misc]
+
+    def test_equality(self) -> None:
+        """Test ThermalState equality comparison."""
+        state1 = ThermalState(
+            chamber_temperature=25.0,
+            case_temperature=30.0,
+            junction_temperature=35.0,
+            timestamp=0.0,
+        )
+        state2 = ThermalState(
+            chamber_temperature=25.0,
+            case_temperature=30.0,
+            junction_temperature=35.0,
+            timestamp=0.0,
+        )
+
+        assert state1 == state2
+
+    def test_hashable(self) -> None:
+        """Test ThermalState is hashable (for use in sets/dicts)."""
+        state = ThermalState(
+            chamber_temperature=25.0,
+            case_temperature=30.0,
+            junction_temperature=35.0,
+            timestamp=0.0,
+        )
+
+        # Should not raise
+        hash(state)
+        {state}  # Can be added to a set
+
+
+class TestElectricalState:
+    """Tests for the ElectricalState dataclass."""
+
+    def test_creation(self) -> None:
+        """Test ElectricalState can be created with valid values."""
+        state = ElectricalState(
+            input_voltage=5.0,
+            output_voltage=3.3,
+            load_current=0.1,
+            quiescent_current=50e-6,
+            power_dissipation=0.17,
+        )
+
+        assert state.input_voltage == 5.0
+        assert state.output_voltage == 3.3
+        assert state.load_current == 0.1
+        assert state.quiescent_current == 50e-6
+        assert state.power_dissipation == 0.17
+
+    def test_immutability(self) -> None:
+        """Test ElectricalState is immutable (frozen dataclass)."""
+        state = ElectricalState(
+            input_voltage=5.0,
+            output_voltage=3.3,
+            load_current=0.1,
+            quiescent_current=50e-6,
+            power_dissipation=0.17,
+        )
+
+        with pytest.raises(AttributeError):
+            state.output_voltage = 1.8  # type: ignore[misc]
+
+    def test_equality(self) -> None:
+        """Test ElectricalState equality comparison."""
+        state1 = ElectricalState(
+            input_voltage=5.0,
+            output_voltage=3.3,
+            load_current=0.1,
+            quiescent_current=50e-6,
+            power_dissipation=0.17,
+        )
+        state2 = ElectricalState(
+            input_voltage=5.0,
+            output_voltage=3.3,
+            load_current=0.1,
+            quiescent_current=50e-6,
+            power_dissipation=0.17,
+        )
+
+        assert state1 == state2
+
+
+class TestPhysicsEngineStub:
+    """Tests for the PhysicsEngine stub."""
+
+    def test_creation_default(self) -> None:
+        """Test PhysicsEngine can be created with defaults."""
+        engine = PhysicsEngine()
+
+        assert engine.dt == pytest.approx(0.01)  # 100Hz -> 10ms
+
+    def test_creation_custom_rate(self) -> None:
+        """Test PhysicsEngine with custom update rate."""
+        engine = PhysicsEngine(update_rate_hz=50.0)
+
+        assert engine.dt == pytest.approx(0.02)  # 50Hz -> 20ms
+
+    def test_step_advances_time(self) -> None:
+        """Test step() advances simulation time."""
+        engine = PhysicsEngine(update_rate_hz=100.0)
+
+        assert engine.simulation_time == pytest.approx(0.0)
+        engine.step()
+        assert engine.simulation_time == pytest.approx(0.01)
+        engine.step()
+        assert engine.simulation_time == pytest.approx(0.02)
+
+    def test_get_thermal_state(self) -> None:
+        """Test get_thermal_state returns ThermalState."""
+        engine = PhysicsEngine()
+
+        state = engine.get_thermal_state()
+
+        assert isinstance(state, ThermalState)
+        assert state.chamber_temperature == 25.0  # Default
+        assert state.timestamp == 0.0
+
+    def test_get_electrical_state(self) -> None:
+        """Test get_electrical_state returns ElectricalState."""
+        engine = PhysicsEngine()
+
+        state = engine.get_electrical_state()
+
+        assert isinstance(state, ElectricalState)
+
+    def test_set_chamber_setpoint(self) -> None:
+        """Test set_chamber_setpoint updates setpoint."""
+        engine = PhysicsEngine()
+
+        engine.set_chamber_setpoint(85.0)
+
+        # Stub doesn't update chamber temp, just stores setpoint
+        state = engine.get_thermal_state()
+        assert state.chamber_temperature == 25.0  # Still at initial
+
+    def test_set_input_voltage(self) -> None:
+        """Test set_input_voltage updates voltage."""
+        engine = PhysicsEngine()
+
+        engine.set_input_voltage(5.0)
+
+        state = engine.get_electrical_state()
+        assert state.input_voltage == 5.0
+
+    def test_set_load_current(self) -> None:
+        """Test set_load_current updates current."""
+        engine = PhysicsEngine()
+        engine.set_output_enabled(True)
+
+        engine.set_load_current(0.1)
+
+        state = engine.get_electrical_state()
+        assert state.load_current == 0.1
+
+    def test_output_disabled_by_default(self) -> None:
+        """Test output is disabled by default."""
+        engine = PhysicsEngine()
+
+        assert not engine.is_output_enabled
+
+    def test_enable_output(self) -> None:
+        """Test set_output_enabled enables output."""
+        engine = PhysicsEngine()
+
+        engine.set_output_enabled(True)
+
+        assert engine.is_output_enabled
+
+    def test_load_current_zero_when_disabled(self) -> None:
+        """Test load current is zero when output disabled."""
+        engine = PhysicsEngine()
+        engine.set_load_current(0.1)
+
+        state = engine.get_electrical_state()
+
+        assert state.load_current == 0.0  # Disabled, so zero

tests/unit/test_power_supply.py

@@ -0,0 +1,352 @@
+"""Unit tests for power supply simulator."""
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.virtual.power_supply import PowerSupplySim
+
+
+class TestPowerSupplySimBasic:
+    """Tests for PowerSupplySim without physics engine."""
+
+    @pytest.fixture
+    def psu(self) -> PowerSupplySim:
+        """Create power supply instance without physics engine."""
+        return PowerSupplySim()
+
+    def test_creation(self, psu: PowerSupplySim) -> None:
+        """Test power supply can be created."""
+        assert psu is not None
+        assert psu.model == "PS-SIM-001"
+        assert psu.manufacturer == "PyDVTATE"
+
+    def test_idn_query(self, psu: PowerSupplySim) -> None:
+        """Test *IDN? returns identification string."""
+        response = psu.process("*IDN?")
+
+        assert "PyDVTATE" in response
+        assert "PS-SIM-001" in response
+
+    def test_rst_command(self, psu: PowerSupplySim) -> None:
+        """Test *RST resets to defaults."""
+        # Set non-default values
+        psu.process("VOLT 12.0")
+        psu.process("CURR 2.0")
+        psu.process("OUTP ON")
+
+        # Reset
+        response = psu.process("*RST")
+        assert response == ""
+
+        # Check defaults restored
+        assert psu.process("VOLT?") == "0.000"
+        assert psu.process("CURR?") == "1.000"
+        assert psu.process("OUTP?") == "0"
+
+    def test_opc_query(self, psu: PowerSupplySim) -> None:
+        """Test *OPC? returns 1."""
+        response = psu.process("*OPC?")
+        assert response == "1"
+
+    def test_unknown_command(self, psu: PowerSupplySim) -> None:
+        """Test unknown command returns error."""
+        response = psu.process("INVALID:CMD")
+
+        assert response.startswith("ERROR:")
+        assert "Unknown command" in response
+
+
+class TestPowerSupplyVoltage:
+    """Tests for VOLT command."""
+
+    @pytest.fixture
+    def psu(self) -> PowerSupplySim:
+        """Create power supply instance without physics engine."""
+        return PowerSupplySim()
+
+    def test_volt_query_default(self, psu: PowerSupplySim) -> None:
+        """Test VOLT? returns default value."""
+        response = psu.process("VOLT?")
+
+        assert response == "0.000"
+
+    def test_volt_set(self, psu: PowerSupplySim) -> None:
+        """Test VOLT sets value."""
+        response = psu.process("VOLT 12.5")
+
+        assert response == ""
+        assert psu.process("VOLT?") == "12.500"
+
+    def test_volt_set_decimal(self, psu: PowerSupplySim) -> None:
+        """Test VOLT accepts decimal values."""
+        psu.process("VOLT 3.3")
+
+        assert psu.process("VOLT?") == "3.300"
+
+    def test_volt_set_negative_fails(self, psu: PowerSupplySim) -> None:
+        """Test VOLT rejects negative values."""
+        response = psu.process("VOLT -5.0")
+
+        assert response.startswith("ERROR:")
+        assert "negative" in response
+
+    def test_volt_set_invalid_value(self, psu: PowerSupplySim) -> None:
+        """Test VOLT with invalid value returns error."""
+        response = psu.process("VOLT abc")
+
+        assert response.startswith("ERROR:")
+        assert "Invalid voltage" in response
+
+    def test_volt_set_no_argument(self, psu: PowerSupplySim) -> None:
+        """Test VOLT without argument returns error."""
+        response = psu.process("VOLT")
+
+        assert response.startswith("ERROR:")
+        assert "requires a value" in response
+
+
+class TestPowerSupplyCurrent:
+    """Tests for CURR command."""
+
+    @pytest.fixture
+    def psu(self) -> PowerSupplySim:
+        """Create power supply instance without physics engine."""
+        return PowerSupplySim()
+
+    def test_curr_query_default(self, psu: PowerSupplySim) -> None:
+        """Test CURR? returns default value."""
+        response = psu.process("CURR?")
+
+        assert response == "1.000"
+
+    def test_curr_set(self, psu: PowerSupplySim) -> None:
+        """Test CURR sets value."""
+        response = psu.process("CURR 0.5")
+
+        assert response == ""
+        assert psu.process("CURR?") == "0.500"
+
+    def test_curr_set_negative_fails(self, psu: PowerSupplySim) -> None:
+        """Test CURR rejects negative values."""
+        response = psu.process("CURR -1.0")
+
+        assert response.startswith("ERROR:")
+        assert "negative" in response
+
+    def test_curr_set_invalid_value(self, psu: PowerSupplySim) -> None:
+        """Test CURR with invalid value returns error."""
+        response = psu.process("CURR xyz")
+
+        assert response.startswith("ERROR:")
+        assert "Invalid current" in response
+
+    def test_curr_set_no_argument(self, psu: PowerSupplySim) -> None:
+        """Test CURR without argument returns error."""
+        response = psu.process("CURR")
+
+        assert response.startswith("ERROR:")
+        assert "requires a value" in response
+
+
+class TestPowerSupplyOutput:
+    """Tests for OUTP command."""
+
+    @pytest.fixture
+    def psu(self) -> PowerSupplySim:
+        """Create power supply instance without physics engine."""
+        return PowerSupplySim()
+
+    def test_outp_query_default(self, psu: PowerSupplySim) -> None:
+        """Test OUTP? returns default value (off)."""
+        response = psu.process("OUTP?")
+
+        assert response == "0"
+
+    def test_outp_set_on(self, psu: PowerSupplySim) -> None:
+        """Test OUTP ON enables output."""
+        response = psu.process("OUTP ON")
+
+        assert response == ""
+        assert psu.process("OUTP?") == "1"
+
+    def test_outp_set_1(self, psu: PowerSupplySim) -> None:
+        """Test OUTP 1 enables output."""
+        psu.process("OUTP 1")
+
+        assert psu.process("OUTP?") == "1"
+
+    def test_outp_set_off(self, psu: PowerSupplySim) -> None:
+        """Test OUTP OFF disables output."""
+        psu.process("OUTP ON")
+        psu.process("OUTP OFF")
+
+        assert psu.process("OUTP?") == "0"
+
+    def test_outp_set_0(self, psu: PowerSupplySim) -> None:
+        """Test OUTP 0 disables output."""
+        psu.process("OUTP ON")
+        psu.process("OUTP 0")
+
+        assert psu.process("OUTP?") == "0"
+
+    def test_outp_set_invalid(self, psu: PowerSupplySim) -> None:
+        """Test OUTP with invalid value returns error."""
+        response = psu.process("OUTP MAYBE")
+
+        assert response.startswith("ERROR:")
+        assert "Invalid output state" in response
+
+    def test_outp_set_no_argument(self, psu: PowerSupplySim) -> None:
+        """Test OUTP without argument returns error."""
+        response = psu.process("OUTP")
+
+        assert response.startswith("ERROR:")
+        assert "requires a value" in response
+
+
+class TestPowerSupplyMeasurement:
+    """Tests for MEAS commands."""
+
+    @pytest.fixture
+    def psu(self) -> PowerSupplySim:
+        """Create power supply instance without physics engine."""
+        return PowerSupplySim()
+
+    def test_meas_volt_when_off(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:VOLT? returns 0 when output is off."""
+        psu.process("VOLT 12.0")
+        response = psu.process("MEAS:VOLT?")
+
+        assert response == "0.000"
+
+    def test_meas_volt_when_on_no_engine(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:VOLT? returns setpoint when on without engine."""
+        psu.process("VOLT 12.0")
+        psu.process("OUTP ON")
+        response = psu.process("MEAS:VOLT?")
+
+        assert response == "12.000"
+
+    def test_meas_volt_as_command_fails(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:VOLT (without ?) returns error."""
+        response = psu.process("MEAS:VOLT 5.0")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+    def test_meas_curr_when_off(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:CURR? returns 0 when output is off."""
+        response = psu.process("MEAS:CURR?")
+
+        assert response == "0.000"
+
+    def test_meas_curr_when_on_no_engine(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:CURR? returns 0 when on without engine."""
+        psu.process("OUTP ON")
+        response = psu.process("MEAS:CURR?")
+
+        assert response == "0.000"
+
+    def test_meas_curr_as_command_fails(self, psu: PowerSupplySim) -> None:
+        """Test MEAS:CURR (without ?) returns error."""
+        response = psu.process("MEAS:CURR 0.1")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestPowerSupplyWithPhysicsEngine:
+    """Tests for PowerSupplySim with physics engine integration."""
+
+    @pytest.fixture
+    def engine(self) -> PhysicsEngine:
+        """Create physics engine instance."""
+        return PhysicsEngine(update_rate_hz=100.0)
+
+    @pytest.fixture
+    def psu(self, engine: PhysicsEngine) -> PowerSupplySim:
+        """Create power supply instance with physics engine."""
+        return PowerSupplySim(physics_engine=engine)
+
+    def test_outp_on_enables_engine_output(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test OUTP ON enables physics engine output."""
+        psu.process("VOLT 5.0")
+        psu.process("OUTP ON")
+
+        assert engine.is_output_enabled is True
+
+    def test_outp_off_disables_engine_output(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test OUTP OFF disables physics engine output."""
+        psu.process("OUTP ON")
+        psu.process("OUTP OFF")
+
+        assert engine.is_output_enabled is False
+
+    def test_volt_updates_engine_when_on(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test VOLT updates engine input voltage when output is on."""
+        psu.process("OUTP ON")
+        psu.process("VOLT 5.0")
+
+        electrical = engine.get_electrical_state()
+        assert electrical.input_voltage == pytest.approx(5.0)
+
+    def test_volt_does_not_update_engine_when_off(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test VOLT does not update engine when output is off."""
+        psu.process("VOLT 5.0")
+
+        electrical = engine.get_electrical_state()
+        assert electrical.input_voltage == pytest.approx(0.0)
+
+    def test_meas_volt_returns_engine_voltage(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:VOLT? returns physics engine voltage."""
+        psu.process("VOLT 5.0")
+        psu.process("OUTP ON")
+
+        response = psu.process("MEAS:VOLT?")
+        assert response == "5.000"
+
+    def test_meas_curr_returns_engine_current(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test MEAS:CURR? returns total current from engine."""
+        psu.process("VOLT 5.0")
+        psu.process("OUTP ON")
+        engine.set_load_current(0.1)
+
+        # Step engine to allow calculations
+        engine.step()
+
+        response = psu.process("MEAS:CURR?")
+        # Should include load current + quiescent current
+        assert float(response) > 0.0
+
+    def test_reset_disables_engine_output(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test *RST disables physics engine output."""
+        psu.process("VOLT 5.0")
+        psu.process("OUTP ON")
+        psu.process("*RST")
+
+        assert engine.is_output_enabled is False
+
+    def test_reset_sets_engine_voltage_zero(
+        self, psu: PowerSupplySim, engine: PhysicsEngine
+    ) -> None:
+        """Test *RST sets physics engine voltage to zero."""
+        psu.process("VOLT 5.0")
+        psu.process("OUTP ON")
+        psu.process("*RST")
+
+        electrical = engine.get_electrical_state()
+        assert electrical.input_voltage == pytest.approx(0.0)

tests/unit/test_scpi_parser.py

@@ -0,0 +1,203 @@
+"""Unit tests for SCPI command parsing."""
+
+import pytest
+
+from py_dvt_ate.instruments.scpi import SCPICommand, SCPIParser
+
+
+class TestSCPICommand:
+    """Tests for the SCPICommand dataclass."""
+
+    def test_creation(self) -> None:
+        """Test SCPICommand can be created with valid values."""
+        cmd = SCPICommand(
+            header="VOLT",
+            arguments=["3.3"],
+            is_query=False,
+        )
+
+        assert cmd.header == "VOLT"
+        assert cmd.arguments == ["3.3"]
+        assert cmd.is_query is False
+
+    def test_keyword_for_command(self) -> None:
+        """Test keyword property for regular command."""
+        cmd = SCPICommand(header="VOLT", arguments=["3.3"], is_query=False)
+
+        assert cmd.keyword == "VOLT"
+
+    def test_keyword_for_query(self) -> None:
+        """Test keyword property strips '?' from query."""
+        cmd = SCPICommand(header="VOLT?", arguments=[], is_query=True)
+
+        assert cmd.keyword == "VOLT"
+
+    def test_keyword_for_nested_command(self) -> None:
+        """Test keyword property for nested SCPI command."""
+        cmd = SCPICommand(header="TEMP:SETPOINT?", arguments=[], is_query=True)
+
+        assert cmd.keyword == "TEMP:SETPOINT"
+
+
+class TestSCPIParser:
+    """Tests for the SCPIParser class."""
+
+    @pytest.fixture
+    def parser(self) -> SCPIParser:
+        """Create parser instance for tests."""
+        return SCPIParser()
+
+    def test_parse_simple_query(self, parser: SCPIParser) -> None:
+        """Test parsing simple query command."""
+        cmd = parser.parse("*IDN?")
+
+        assert cmd.header == "*IDN?"
+        assert cmd.arguments == []
+        assert cmd.is_query is True
+        assert cmd.keyword == "*IDN"
+
+    def test_parse_simple_command(self, parser: SCPIParser) -> None:
+        """Test parsing simple command without arguments."""
+        cmd = parser.parse("*RST")
+
+        assert cmd.header == "*RST"
+        assert cmd.arguments == []
+        assert cmd.is_query is False
+        assert cmd.keyword == "*RST"
+
+    def test_parse_command_with_single_argument(self, parser: SCPIParser) -> None:
+        """Test parsing command with single numeric argument."""
+        cmd = parser.parse("VOLT 3.3")
+
+        assert cmd.header == "VOLT"
+        assert cmd.arguments == ["3.3"]
+        assert cmd.is_query is False
+
+    def test_parse_command_with_multiple_arguments(self, parser: SCPIParser) -> None:
+        """Test parsing command with comma-separated arguments."""
+        cmd = parser.parse("CONF:VOLT:DC 10,0.001")
+
+        assert cmd.header == "CONF:VOLT:DC"
+        assert cmd.arguments == ["10", "0.001"]
+        assert cmd.is_query is False
+
+    def test_parse_nested_scpi_command(self, parser: SCPIParser) -> None:
+        """Test parsing nested SCPI command hierarchy."""
+        cmd = parser.parse("TEMP:SETPOINT 85.0")
+
+        assert cmd.header == "TEMP:SETPOINT"
+        assert cmd.arguments == ["85.0"]
+        assert cmd.is_query is False
+        assert cmd.keyword == "TEMP:SETPOINT"
+
+    def test_parse_nested_scpi_query(self, parser: SCPIParser) -> None:
+        """Test parsing nested SCPI query."""
+        cmd = parser.parse("TEMP:SETPOINT?")
+
+        assert cmd.header == "TEMP:SETPOINT?"
+        assert cmd.arguments == []
+        assert cmd.is_query is True
+
+    def test_parse_ieee_common_commands(self, parser: SCPIParser) -> None:
+        """Test parsing IEEE 488.2 common commands."""
+        # Identity query
+        cmd = parser.parse("*IDN?")
+        assert cmd.is_query is True
+        assert cmd.keyword == "*IDN"
+
+        # Reset
+        cmd = parser.parse("*RST")
+        assert cmd.is_query is False
+        assert cmd.keyword == "*RST"
+
+        # Clear status
+        cmd = parser.parse("*CLS")
+        assert cmd.is_query is False
+        assert cmd.keyword == "*CLS"
+
+        # Operation complete query
+        cmd = parser.parse("*OPC?")
+        assert cmd.is_query is True
+        assert cmd.keyword == "*OPC"
+
+    def test_parse_strips_whitespace(self, parser: SCPIParser) -> None:
+        """Test parser strips leading and trailing whitespace."""
+        cmd = parser.parse("  VOLT 3.3  ")
+
+        assert cmd.header == "VOLT"
+        assert cmd.arguments == ["3.3"]
+
+    def test_parse_strips_argument_whitespace(self, parser: SCPIParser) -> None:
+        """Test parser strips whitespace from arguments."""
+        cmd = parser.parse("CONF:VOLT:DC  10 , 0.001 ")
+
+        assert cmd.arguments == ["10", "0.001"]
+
+    def test_parse_empty_string(self, parser: SCPIParser) -> None:
+        """Test parsing empty string returns empty command."""
+        cmd = parser.parse("")
+
+        assert cmd.header == ""
+        assert cmd.arguments == []
+        assert cmd.is_query is False
+
+    def test_parse_whitespace_only(self, parser: SCPIParser) -> None:
+        """Test parsing whitespace-only string returns empty command."""
+        cmd = parser.parse("   ")
+
+        assert cmd.header == ""
+        assert cmd.arguments == []
+        assert cmd.is_query is False
+
+    def test_parse_output_on_off(self, parser: SCPIParser) -> None:
+        """Test parsing output enable/disable commands."""
+        cmd_on = parser.parse("OUTP ON")
+        assert cmd_on.arguments == ["ON"]
+
+        cmd_off = parser.parse("OUTP OFF")
+        assert cmd_off.arguments == ["OFF"]
+
+        cmd_1 = parser.parse("OUTP 1")
+        assert cmd_1.arguments == ["1"]
+
+        cmd_0 = parser.parse("OUTP 0")
+        assert cmd_0.arguments == ["0"]
+
+    def test_parse_channel_select(self, parser: SCPIParser) -> None:
+        """Test parsing channel selection commands."""
+        cmd = parser.parse("INST:SEL CH1")
+
+        assert cmd.header == "INST:SEL"
+        assert cmd.arguments == ["CH1"]
+
+    def test_parse_measurement_query(self, parser: SCPIParser) -> None:
+        """Test parsing measurement query commands."""
+        cmd = parser.parse("MEAS:VOLT:DC?")
+
+        assert cmd.header == "MEAS:VOLT:DC?"
+        assert cmd.is_query is True
+        assert cmd.keyword == "MEAS:VOLT:DC"
+
+    def test_parse_measurement_with_range(self, parser: SCPIParser) -> None:
+        """Test parsing measurement query with range argument."""
+        cmd = parser.parse("MEAS:VOLT:DC? AUTO")
+
+        assert cmd.header == "MEAS:VOLT:DC?"
+        assert cmd.arguments == ["AUTO"]
+        assert cmd.is_query is True
+
+    def test_parse_system_error_query(self, parser: SCPIParser) -> None:
+        """Test parsing system error query."""
+        cmd = parser.parse("SYST:ERR?")
+
+        assert cmd.header == "SYST:ERR?"
+        assert cmd.is_query is True
+        assert cmd.keyword == "SYST:ERR"
+
+    def test_parse_nplc_setting(self, parser: SCPIParser) -> None:
+        """Test parsing NPLC (integration time) command."""
+        cmd = parser.parse("SENS:VOLT:DC:NPLC 10")
+
+        assert cmd.header == "SENS:VOLT:DC:NPLC"
+        assert cmd.arguments == ["10"]
+        assert cmd.is_query is False

tests/unit/test_thermal_chamber.py

@@ -0,0 +1,215 @@
+"""Unit tests for thermal chamber simulator."""
+
+import pytest
+
+from py_dvt_ate.simulation.physics.engine import PhysicsEngine
+from py_dvt_ate.simulation.virtual.chamber import ThermalChamberSim
+
+
+class TestThermalChamberSimBasic:
+    """Tests for ThermalChamberSim without physics engine."""
+
+    @pytest.fixture
+    def chamber(self) -> ThermalChamberSim:
+        """Create chamber instance without physics engine."""
+        return ThermalChamberSim()
+
+    def test_creation(self, chamber: ThermalChamberSim) -> None:
+        """Test chamber can be created."""
+        assert chamber is not None
+        assert chamber.model == "TC-SIM-001"
+        assert chamber.manufacturer == "PyDVTATE"
+
+    def test_idn_query(self, chamber: ThermalChamberSim) -> None:
+        """Test *IDN? returns identification string."""
+        response = chamber.process("*IDN?")
+
+        assert "PyDVTATE" in response
+        assert "TC-SIM-001" in response
+
+    def test_rst_command(self, chamber: ThermalChamberSim) -> None:
+        """Test *RST resets to defaults."""
+        # Set non-default value
+        chamber.process("TEMP:SETPOINT 85.0")
+        assert chamber.process("TEMP:SETPOINT?") == "85.00"
+
+        # Reset
+        response = chamber.process("*RST")
+        assert response == ""
+        assert chamber.process("TEMP:SETPOINT?") == "25.00"
+
+    def test_opc_query(self, chamber: ThermalChamberSim) -> None:
+        """Test *OPC? returns 1."""
+        response = chamber.process("*OPC?")
+        assert response == "1"
+
+    def test_unknown_command(self, chamber: ThermalChamberSim) -> None:
+        """Test unknown command returns error."""
+        response = chamber.process("INVALID:CMD")
+
+        assert response.startswith("ERROR:")
+        assert "Unknown command" in response
+
+
+class TestThermalChamberSetpoint:
+    """Tests for TEMP:SETPOINT command."""
+
+    @pytest.fixture
+    def chamber(self) -> ThermalChamberSim:
+        """Create chamber instance without physics engine."""
+        return ThermalChamberSim()
+
+    def test_setpoint_query_default(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:SETPOINT? returns default value."""
+        response = chamber.process("TEMP:SETPOINT?")
+
+        assert response == "25.00"
+
+    def test_setpoint_set(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:SETPOINT sets value."""
+        response = chamber.process("TEMP:SETPOINT 85.0")
+
+        assert response == ""
+        assert chamber.process("TEMP:SETPOINT?") == "85.00"
+
+    def test_setpoint_set_negative(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:SETPOINT accepts negative values."""
+        chamber.process("TEMP:SETPOINT -40.0")
+
+        assert chamber.process("TEMP:SETPOINT?") == "-40.00"
+
+    def test_setpoint_set_invalid_value(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:SETPOINT with invalid value returns error."""
+        response = chamber.process("TEMP:SETPOINT abc")
+
+        assert response.startswith("ERROR:")
+        assert "Invalid temperature" in response
+
+    def test_setpoint_set_no_argument(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:SETPOINT without argument returns error."""
+        response = chamber.process("TEMP:SETPOINT")
+
+        assert response.startswith("ERROR:")
+        assert "requires a value" in response
+
+
+class TestThermalChamberActual:
+    """Tests for TEMP:ACTUAL? query."""
+
+    @pytest.fixture
+    def chamber(self) -> ThermalChamberSim:
+        """Create chamber instance without physics engine."""
+        return ThermalChamberSim()
+
+    def test_actual_query_without_engine(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:ACTUAL? returns setpoint when no physics engine."""
+        chamber.process("TEMP:SETPOINT 50.0")
+        response = chamber.process("TEMP:ACTUAL?")
+
+        # Without physics engine, returns setpoint
+        assert response == "50.00"
+
+    def test_actual_as_command_fails(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:ACTUAL (without ?) returns error."""
+        response = chamber.process("TEMP:ACTUAL 25.0")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestThermalChamberStability:
+    """Tests for TEMP:STAB? query."""
+
+    @pytest.fixture
+    def chamber(self) -> ThermalChamberSim:
+        """Create chamber instance without physics engine."""
+        return ThermalChamberSim()
+
+    def test_stab_query_without_engine(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:STAB? returns 1 when no physics engine."""
+        response = chamber.process("TEMP:STAB?")
+
+        # Without physics engine, assume stable
+        assert response == "1"
+
+    def test_stab_as_command_fails(self, chamber: ThermalChamberSim) -> None:
+        """Test TEMP:STAB (without ?) returns error."""
+        response = chamber.process("TEMP:STAB 1")
+
+        assert response.startswith("ERROR:")
+        assert "query only" in response
+
+
+class TestThermalChamberWithPhysicsEngine:
+    """Tests for ThermalChamberSim with physics engine integration."""
+
+    @pytest.fixture
+    def engine(self) -> PhysicsEngine:
+        """Create physics engine instance."""
+        return PhysicsEngine(update_rate_hz=100.0)
+
+    @pytest.fixture
+    def chamber(self, engine: PhysicsEngine) -> ThermalChamberSim:
+        """Create chamber instance with physics engine."""
+        return ThermalChamberSim(physics_engine=engine)
+
+    def test_setpoint_updates_engine(
+        self, chamber: ThermalChamberSim, engine: PhysicsEngine
+    ) -> None:
+        """Test TEMP:SETPOINT updates physics engine."""
+        chamber.process("TEMP:SETPOINT 85.0")
+
+        # Step the engine and check thermal state
+        thermal = engine.get_thermal_state()
+        # Initial chamber temp is 25, will start moving towards 85
+        assert thermal.chamber_temperature == pytest.approx(25.0, abs=0.1)
+
+        # After many steps, should approach setpoint
+        for _ in range(10000):  # 100 seconds at 100Hz
+            engine.step()
+
+        thermal = engine.get_thermal_state()
+        # Should be closer to setpoint (but not quite there due to time constant)
+        assert thermal.chamber_temperature > 80.0
+
+    def test_actual_query_returns_engine_temperature(
+        self, chamber: ThermalChamberSim, engine: PhysicsEngine
+    ) -> None:
+        """Test TEMP:ACTUAL? returns physics engine temperature."""
+        response = chamber.process("TEMP:ACTUAL?")
+
+        # Should match initial chamber temperature
+        assert response == "25.00"
+
+    def test_stability_when_at_setpoint(
+        self, chamber: ThermalChamberSim, engine: PhysicsEngine
+    ) -> None:
+        """Test TEMP:STAB? returns 1 when at setpoint."""
+        # Default setpoint is 25, engine starts at 25
+        response = chamber.process("TEMP:STAB?")
+
+        assert response == "1"
+
+    def test_stability_when_settling(
+        self, chamber: ThermalChamberSim, engine: PhysicsEngine
+    ) -> None:
+        """Test TEMP:STAB? returns 0 when settling."""
+        # Set new setpoint far from current temperature
+        chamber.process("TEMP:SETPOINT 85.0")
+
+        # Step once to ensure engine updates
+        engine.step()
+
+        # Should not be stable yet
+        response = chamber.process("TEMP:STAB?")
+        assert response == "0"
+
+    def test_reset_updates_engine(
+        self, chamber: ThermalChamberSim, engine: PhysicsEngine
+    ) -> None:
+        """Test *RST resets both chamber and engine setpoint."""
+        chamber.process("TEMP:SETPOINT 85.0")
+        chamber.process("*RST")
+
+        # Check setpoint is back to default
+        assert chamber.process("TEMP:SETPOINT?") == "25.00"