Add multimeter simulator tests

Comprehensive test coverage for MultimeterSim including MEAS:VOLT:DC,
MEAS:CURR:DC, CONF, and READ commands. Tests both standalone operation
and physics engine integration including temperature-dependent measurements.

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