Release v0.1.0-alpha.1

Physics engine working milestone:
- Thermal-electrical coupling simulation
- LDO DUT model with temperature dependence
- Comprehensive test suite

CHANGELOG.md

@@ -7,6 +7,20 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [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
@@ -30,5 +44,5 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 | 0.1.0-beta.1 | TBD | HAL complete |
 | 0.1.0-alpha.3 | TBD | Network ready |
 | 0.1.0-alpha.2 | TBD | 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/
-│   └── thermaulate/
+├── src/py_dvt_ate/
+│   ├── __init__.py                     # Package version
+│   ├── py.typed                        # PEP 561 marker
+│   │
+│   ├── instruments/                    # INSTRUMENT CONTROL (reusable)
+│   │   ├── __init__.py
+│   │   ├── interfaces.py               # IThermalChamber, IPowerSupply, IMultimeter
+│   │   ├── scpi.py                     # SCPI parser (shared protocol)
+│   │   ├── factory.py                  # Creates instrument sets from config
+│   │   ├── 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                 # Base driver
+│   │       ├── chamber.py              # Thermal chamber driver
+│   │       ├── power_supply.py         # PSU driver
+│   │       └── multimeter.py           # DMM driver
+│   │
+│   ├── simulation/                     # PHYSICS SIMULATION (dev/test only)
+│   │   ├── __init__.py
+│   │   ├── server.py                   # TCP server hosting virtual instruments
+│   │   ├── physics/                    # Physics engine
+│   │   │   ├── __init__.py
+│   │   │   ├── engine.py               # Main simulation loop
+│   │   │   ├── 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
+│   │
+│   ├── framework/                      # TEST FRAMEWORK (reusable)
+│   │   ├── __init__.py
+│   │   ├── runner.py                   # Test sequencer
+│   │   ├── context.py                  # Runtime context
+│   │   ├── logger.py                   # Measurement logging
+│   │   ├── limits.py                   # Pass/fail evaluation
+│   │   └── models.py                   # Framework models
+│   │
+│   ├── tests/                          # DVT TEST IMPLEMENTATIONS
+│   │   ├── __init__.py
+│   │   ├── base.py                     # Base test class
+│   │   ├── thermal/                    # Thermal characterisation tests
+│   │   │   ├── __init__.py
+│   │   │   └── tempco.py               # Temperature coefficient test
+│   │   └── electrical/                 # Electrical characterisation tests
+│   │       ├── __init__.py
+│   │       └── load_regulation.py      # Load regulation test
+│   │
+│   ├── data/                           # DATA PERSISTENCE (shared)
+│   │   ├── __init__.py
+│   │   ├── repository.py               # Data access layer
+│   │   └── models.py                   # Data models
+│   │
+│   ├── reporting/                      # REPORT GENERATION (standalone)
+│   │   ├── __init__.py
+│   │   ├── generator.py                # Report generator
+│   │   └── templates/                  # Report templates
+│   │
+│   └── app/                            # APPLICATION ENTRY POINTS
 │       ├── __init__.py
-│       ├── py.typed                     # PEP 561 marker
-│       │
-│       ├── physics/                     # Physics simulation engine
-│       │   ├── __init__.py
-│       │   ├── engine.py                # Main physics loop
-│       │   ├── thermal.py               # Thermal domain model
-│       │   ├── electrical.py            # Electrical domain model
-│       │   └── dut/
-│       │       ├── __init__.py
-│       │       ├── base.py              # DUT base class
-│       │       └── ldo.py               # LDO voltage regulator model
-│       │
-│       ├── instruments/                 # Virtual instrument implementations
-│       │   ├── __init__.py
-│       │   ├── base.py                  # Instrument base class
-│       │   ├── scpi_parser.py           # SCPI command parser
-│       │   ├── thermal_chamber.py       # Thermal chamber simulator
-│       │   ├── power_supply.py          # Power supply simulator
-│       │   └── multimeter.py            # DMM simulator
-│       │
-│       ├── server/                      # Simulation server
-│       │   ├── __init__.py
-│       │   ├── tcp_server.py            # Async TCP server
-│       │   └── main.py                  # Server entry point
-│       │
-│       ├── transport/                   # Communication layer
-│       │   ├── __init__.py
-│       │   ├── base.py                  # Transport protocol
-│       │   ├── tcp.py                   # TCP/IP implementation
-│       │   └── async_tcp.py             # Async TCP implementation
-│       │
-│       ├── drivers/                     # Instrument SCPI drivers
-│       │   ├── __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
-│       │   ├── __init__.py
-│       │   ├── repository.py            # Data access layer
-│       │   ├── models.py                # Data models
-│       │   └── migrations/              # Schema migrations
-│       │
-│       ├── reporting/                   # Report generation (Phase 3)
-│       │   ├── __init__.py
-│       │   ├── generator.py             # Report generator
-│       │   ├── pdf.py                   # PDF output
-│       │   ├── html.py                  # HTML output
-│       │   └── templates/               # Report templates
-│       │
-│       ├── api/                         # REST API (Phase 2)
-│       │   ├── __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
+│       ├── cli.py                      # Command-line interface
+│       ├── config.py                   # YAML loading
+│       └── dashboard/                  # Streamlit dashboard
 │           ├── __init__.py
-│           ├── models.py                # Pydantic config models
-│           └── loader.py                # Config file loader
+│           └── app.py                  # Main Streamlit app
 │
-├── tests/                               # Test suite
-│   ├── conftest.py                      # pytest fixtures
-│   ├── unit/
-│   │   ├── test_physics_engine.py
-│   │   ├── test_scpi_parser.py
-│   │   ├── test_thermal_model.py
-│   │   └── ...
-│   └── integration/
-│       ├── test_instrument_communication.py
-│       ├── test_tempco_sequence.py
-│       └── ...
+├── tests/                              # pytest test suite
+│   ├── conftest.py                     # pytest fixtures
+│   ├── unit/                           # Unit tests
+│   └── integration/                    # Integration tests
 │
-├── config/                              # Configuration files
-│   ├── default.yaml                     # Default configuration
-│   └── example_pyvisa.yaml              # Example for real hardware
+├── config/                             # Configuration files
+│   └── default.yaml                    # Default configuration
 │
-├── docker/
-│   ├── Dockerfile.server                # Simulation server image
-│   ├── Dockerfile.app                   # Test application image
-│   └── docker-compose.yml               # Full stack orchestration
-│
-└── scripts/
-    ├── demo.py                          # Demo script
-    └── run_tempco.py                    # Example test execution
+└── docker/                             # Docker deployment
+    ├── Dockerfile.server               # Simulation server image
+    ├── Dockerfile.app                  # Test application image
+    └── docker-compose.yml              # Full stack orchestration
 ```
 
 ### 2.2 Package Dependencies
 
 ```
-thermaulate/
-├── cli/           ──────────────────────────────────────────────┐
-├── api/           ──────────────────────────────────────────────┤
-├── dashboard/     ──────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    PRESENTATION                          │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                              ▼                                  │
-├── executive/     ◄───────────────────────────────────────────────┤
-├── tests/         ◄───────────────────────────────────────────────┤
-├── reporting/     ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    APPLICATION                           │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                              ▼                                  │
-├── hal/interfaces ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    DOMAIN (Abstractions)                 │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                              │                                  │
-│                    implements│                                  │
-│                              ▼                                  │
-├── hal/impl       ◄───────────────────────────────────────────────┤
-├── drivers/       ◄───────────────────────────────────────────────┤
-├── transport/     ◄───────────────────────────────────────────────┤
-├── data/          ◄───────────────────────────────────────────────┤
-│                                                                 │
-│   ┌─────────────────────────────────────────────────────────┐  │
-│   │                    INFRASTRUCTURE                        │  │
-│   └─────────────────────────────────────────────────────────┘  │
-│                                                                 │
-└─────────────────────────────────────────────────────────────────┘
+Dependency Graph:
 
-SIMULATION SERVER (Separate Process):
-├── physics/       ◄─── Pure domain logic, no external dependencies
-├── instruments/   ◄─── Depends on physics
-└── server/        ◄─── Depends on instruments
+app/ ──────────────▶ framework/ ──────────────▶ 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 |
-| ThermalModel | `thermal.py` | Heat transfer calculations |
-| ElectricalModel | `electrical.py` | Current/voltage relationships |
-| DUTBase | `dut/base.py` | Abstract DUT interface |
-| LDOModel | `dut/ldo.py` | LDO voltage regulator implementation |
+| Interfaces | `instruments/interfaces.py` | IThermalChamber, IPowerSupply, IMultimeter protocols |
+| SCPIParser | `instruments/scpi.py` | Parse SCPI command strings |
+| Factory | `instruments/factory.py` | Create instrument sets from config |
+| Transport | `instruments/transport/` | TCP, VISA connection layer |
+| 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 |
-| SCPIParser | `scpi_parser.py` | Parse SCPI command strings |
-| ThermalChamberSim | `thermal_chamber.py` | Chamber simulation |
-| PowerSupplySim | `power_supply.py` | PSU simulation |
-| MultimeterSim | `multimeter.py` | DMM simulation |
-
-**Command Processing Flow**:
-```
-SCPI String → Parser → Command Object → Instrument Handler → Response
-```
+| TestRunner | `framework/runner.py` | Sequences test steps |
+| TestContext | `framework/context.py` | Runtime context |
+| TestLogger | `framework/logger.py` | Measurement logging |
+| LimitChecker | `framework/limits.py` | Pass/fail evaluation |
+| Models | `framework/models.py` | TestStatus, TestResult, etc. |
 
 ---
 
-### 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 |
-| TCPTransport | `tcp.py` | Synchronous TCP implementation |
-| AsyncTCPTransport | `async_tcp.py` | Async TCP implementation |
+| Repository | `data/repository.py` | Data access layer |
+| Models | `data/models.py` | TestRun, Measurement dataclasses |
 
 ---
 
-### 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 |
-| ThermalChamberDriver | `thermal_chamber.py` | Chamber SCPI commands |
-| PowerSupplyDriver | `power_supply.py` | PSU SCPI commands |
-| MultimeterDriver | `multimeter.py` | DMM SCPI commands |
+| Generator | `reporting/generator.py` | Creates reports from data |
+| Templates | `reporting/templates/` | Report templates |
 
 ---
 
-### 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 |
-| InstrumentFactory | `factory.py` | Creates instrument sets from config |
-| HAL Implementations | `impl/*.py` | Concrete HAL classes |
-
----
-
-### 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 |
+| CLI | `app/cli.py` | Command-line interface (Typer) |
+| Config | `app/config.py` | YAML loading, instance creation |
+| Dashboard | `app/dashboard/app.py` | Streamlit application |
 
 ---
 
 ## 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 thermaulate.drivers.thermal_chamber import ThermalChamberDriver
-        from thermaulate.drivers.power_supply import PowerSupplyDriver
-        from thermaulate.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
+        from py_dvt_ate.instruments.transport.tcp import TCPTransport
+        from py_dvt_ate.instruments.drivers.chamber import ThermalChamberDriver
+        from py_dvt_ate.instruments.drivers.power_supply import PowerSupplyDriver
+        from py_dvt_ate.instruments.drivers.multimeter import MultimeterDriver
 
         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)),
-            psu=PowerSupplyHAL(PowerSupplyDriver(psu_transport)),
-            dmm=MultimeterHAL(MultimeterDriver(dmm_transport)),
+            chamber=ThermalChamberDriver(chamber_transport),
+            psu=PowerSupplyDriver(psu_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"
-thermaulate-server = "thermaulate.server.main:main"
-thermaulate-dashboard = "thermaulate.dashboard.app:main"
+py_dvt_ate = "py_dvt_ate.cli.main:app"
+py_dvt_ate-server = "py_dvt_ate.server.main: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/physics/models.py
+- Create src/py_dvt_ate/simulation/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/physics/dut/base.py
+- Create src/py_dvt_ate/simulation/physics/models/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/dashboard/app.py
+- Create src/py_dvt_ate/app/dashboard/__init__.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/server/tcp_server.py
+- Create src/py_dvt_ate/simulation/__init__.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/transport/base.py
+- Create src/py_dvt_ate/instruments/transport/__init__.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/drivers/base.py
+- Create src/py_dvt_ate/instruments/drivers/__init__.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/drivers/multimeter.py
+- Create src/py_dvt_ate/instruments/drivers/power_supply.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
-- Create src/py_dvt_ate/hal/__init__.py
-- Create src/py_dvt_ate/hal/interfaces.py
-- Define IThermalChamber, IPowerSupply, IMultimeter
-- **Commit:** "Add HAL protocol definitions"
+### Task 11.1: Define instrument interface protocols
+- Create src/py_dvt_ate/instruments/interfaces.py
+- Define IThermalChamber, IPowerSupply, IMultimeter protocols
+- **Commit:** "Add instrument interface protocols"
 
-### Task 11.2: Implement HAL wrappers
-- Create src/py_dvt_ate/hal/impl/__init__.py
-- Create HAL implementation classes
-- Wrap drivers with HAL interface
-- **Commit:** "Add HAL implementations"
+### Task 11.2: Ensure drivers implement interfaces
+- Update drivers to satisfy Protocol interfaces
+- Add type hints for interface compliance
+- **Commit:** "Implement instrument interfaces in drivers"
 
 ### 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
-- Create tests/unit/test_hal.py
+### Task 11.4: Add instrument interface tests
+- 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/config/models.py
-- Pydantic models for all config sections
+- Create src/py_dvt_ate/app/config.py
+- Define 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/executive/models.py
+- Create src/py_dvt_ate/framework/__init__.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
-- Create src/py_dvt_ate/executive/sequencer.py
+### Task 14.4: Implement test runner
+- 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)
-physics/dut/base.py        → models.py
-physics/dut/ldo.py         → base.py, models.py
-physics/thermal.py         → models.py
-physics/engine.py          → models.py, thermal.py, dut/base.py
+simulation/physics/models.py         → (none)
+simulation/physics/models/base.py    → models.py
+simulation/physics/models/ldo.py     → base.py, models.py
+simulation/physics/thermal.py        → models.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/base.py        → scpi_parser.py
-instruments/*_sim.py       → base.py, physics/engine.py
+instruments/scpi.py                  → (none)
+simulation/virtual/base.py           → instruments/scpi.py
+simulation/virtual/*.py              → base.py, simulation/physics/engine.py
 
-transport/base.py          → (none)
-transport/tcp.py           → base.py
+instruments/transport/base.py        → (none)
+instruments/transport/tcp.py         → base.py
 
-drivers/base.py            → transport/base.py
-drivers/*.py               → base.py
+instruments/drivers/base.py          → instruments/transport/base.py
+instruments/drivers/*.py             → base.py
 
-hal/interfaces.py          → (none)
-hal/impl/*.py              → interfaces.py, drivers/*.py
-hal/factory.py             → interfaces.py, impl/*.py
+instruments/interfaces.py            → (none)
+instruments/factory.py               → interfaces.py, drivers/*.py
 
-config/models.py           → (none)
-config/loader.py           → models.py
+app/config.py                        → (none)
 
-data/models.py             → (none)
-data/repository.py         → models.py
+data/models.py                       → (none)
+data/repository.py                   → models.py
 
-executive/models.py        → hal/interfaces.py
-executive/*.py             → models.py, data/repository.py
+framework/context.py                 → instruments/interfaces.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-server = "py_dvt_ate.server.main:main"
-py-dvt-ate-dashboard = "py_dvt_ate.dashboard.app:main"
+py-dvt-ate = "py_dvt_ate.app.cli:app"
+py-dvt-ate-server = "py_dvt_ate.simulation.server:main"
+py-dvt-ate-dashboard = "py_dvt_ate.app.dashboard.app:main"
 
 [build-system]
 requires = ["hatchling"]

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.1"

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/dashboard/__init__.py

@@ -0,0 +1,5 @@
+"""Streamlit dashboard for real-time monitoring.
+
+Provides visualisation of instrument status, test progress,
+and historical results.
+"""

src/py_dvt_ate/cli/__init__.py

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

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/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 +1,5 @@
+"""Physics simulation package.
+
+Provides virtual instruments backed by a coupled thermal-electrical
+physics engine. Used for development and testing without real hardware.
+"""

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/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/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/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