feat(sensors): add sensor framework for pipeline integration

- Add Sensor base class with value emission
- Add SensorRegistry for discovery
- Add SensorStage adapter for pipeline
- Add MicSensor (self-contained, no external deps)
- Add OscillatorSensor for testing
- Add sensor param bindings to effects

engine/sensors/__init__.py

@@ -0,0 +1,186 @@
+"""
+Sensor framework - PureData-style real-time input system.
+
+Sensors are data sources that emit values over time, similar to how
+PureData objects emit signals. Effects can bind to sensors to modulate
+their parameters dynamically.
+
+Architecture:
+- Sensor: Base class for all sensors (mic, camera, ntfy, OSC, etc.)
+- SensorRegistry: Global registry for sensor discovery
+- SensorStage: Pipeline stage wrapper for sensors
+- Effect param_bindings: Declarative sensor-to-param routing
+
+Example:
+    class GlitchEffect(EffectPlugin):
+        param_bindings = {
+            "intensity": {"sensor": "mic", "transform": "linear"},
+        }
+
+This binds the mic sensor to the glitch intensity parameter.
+"""
+
+from abc import ABC, abstractmethod
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any
+
+if TYPE_CHECKING:
+    from engine.pipeline.core import PipelineContext
+
+
+@dataclass
+class SensorValue:
+    """A sensor reading with metadata."""
+
+    sensor_name: str
+    value: float
+    timestamp: float
+    unit: str = ""
+
+
+class Sensor(ABC):
+    """Abstract base class for sensors.
+
+    Sensors are real-time data sources that emit values. They can be:
+    - Physical: mic, camera, joystick, MIDI, OSC
+    - Virtual: ntfy, timer, random, noise
+
+    Each sensor has a name and emits SensorValue objects.
+    """
+
+    name: str
+    unit: str = ""
+
+    @property
+    def available(self) -> bool:
+        """Whether the sensor is currently available."""
+        return True
+
+    @abstractmethod
+    def read(self) -> SensorValue | None:
+        """Read current sensor value.
+
+        Returns:
+            SensorValue if available, None if sensor is not ready.
+        """
+        ...
+
+    @abstractmethod
+    def start(self) -> bool:
+        """Start the sensor.
+
+        Returns:
+            True if started successfully.
+        """
+        ...
+
+    @abstractmethod
+    def stop(self) -> None:
+        """Stop the sensor and release resources."""
+        ...
+
+
+class SensorRegistry:
+    """Global registry for sensors.
+
+    Provides:
+    - Registration of sensor instances
+    - Lookup by name
+    - Global start/stop
+    """
+
+    _sensors: dict[str, Sensor] = {}
+    _started: bool = False
+
+    @classmethod
+    def register(cls, sensor: Sensor) -> None:
+        """Register a sensor instance."""
+        cls._sensors[sensor.name] = sensor
+
+    @classmethod
+    def get(cls, name: str) -> Sensor | None:
+        """Get a sensor by name."""
+        return cls._sensors.get(name)
+
+    @classmethod
+    def list_sensors(cls) -> list[str]:
+        """List all registered sensor names."""
+        return list(cls._sensors.keys())
+
+    @classmethod
+    def start_all(cls) -> bool:
+        """Start all sensors.
+
+        Returns:
+            True if all sensors started successfully.
+        """
+        if cls._started:
+            return True
+
+        all_started = True
+        for sensor in cls._sensors.values():
+            if sensor.available and not sensor.start():
+                all_started = False
+
+        cls._started = all_started
+        return all_started
+
+    @classmethod
+    def stop_all(cls) -> None:
+        """Stop all sensors."""
+        for sensor in cls._sensors.values():
+            sensor.stop()
+        cls._started = False
+
+    @classmethod
+    def read_all(cls) -> dict[str, float]:
+        """Read all sensor values.
+
+        Returns:
+            Dict mapping sensor name to current value.
+        """
+        result = {}
+        for name, sensor in cls._sensors.items():
+            value = sensor.read()
+            if value:
+                result[name] = value.value
+        return result
+
+
+class SensorStage:
+    """Pipeline stage wrapper for sensors.
+
+    Provides sensor data to the pipeline context.
+    """
+
+    def __init__(self, sensor: Sensor, name: str | None = None):
+        self._sensor = sensor
+        self.name = name or sensor.name
+        self.category = "sensor"
+        self.optional = True
+
+    @property
+    def capabilities(self) -> set[str]:
+        return {f"sensor.{self.name}"}
+
+    @property
+    def dependencies(self) -> set[str]:
+        return set()
+
+    def init(self, ctx: "PipelineContext") -> bool:
+        return self._sensor.start()
+
+    def process(self, data: Any, ctx: "PipelineContext") -> Any:
+        value = self._sensor.read()
+        if value:
+            ctx.set_state(f"sensor.{self.name}", value.value)
+            ctx.set_state(f"sensor.{self.name}.full", value)
+        return data
+
+    def cleanup(self) -> None:
+        self._sensor.stop()
+
+
+def create_sensor_stage(sensor: Sensor, name: str | None = None) -> SensorStage:
+    """Create a pipeline stage from a sensor."""
+    return SensorStage(sensor, name)

engine/sensors/mic.py

@@ -0,0 +1,147 @@
+"""
+Mic sensor - audio input as a pipeline sensor.
+
+Self-contained implementation that handles audio input directly,
+with graceful degradation if sounddevice is unavailable.
+"""
+
+import atexit
+import time
+from collections.abc import Callable
+from dataclasses import dataclass
+from datetime import datetime
+from typing import Any
+
+try:
+    import numpy as np
+    import sounddevice as sd
+
+    _HAS_AUDIO = True
+except Exception:
+    _HAS_AUDIO = False
+    np = None  # type: ignore
+    sd = None  # type: ignore
+
+
+from engine.events import MicLevelEvent
+from engine.sensors import Sensor, SensorRegistry, SensorValue
+
+
+@dataclass
+class AudioConfig:
+    """Configuration for audio input."""
+
+    threshold_db: float = 50.0
+    sample_rate: float = 44100.0
+    block_size: int = 1024
+
+
+class MicSensor(Sensor):
+    """Microphone sensor for pipeline integration.
+
+    Self-contained implementation with graceful degradation.
+    No external dependencies required - works with or without sounddevice.
+    """
+
+    def __init__(self, threshold_db: float = 50.0, name: str = "mic"):
+        self.name = name
+        self.unit = "dB"
+        self._config = AudioConfig(threshold_db=threshold_db)
+        self._db: float = -99.0
+        self._stream: Any = None
+        self._subscribers: list[Callable[[MicLevelEvent], None]] = []
+
+    @property
+    def available(self) -> bool:
+        """Check if audio input is available."""
+        return _HAS_AUDIO and self._stream is not None
+
+    def start(self) -> bool:
+        """Start the microphone stream."""
+        if not _HAS_AUDIO:
+            return False
+
+        try:
+            self._stream = sd.InputStream(
+                samplerate=self._config.sample_rate,
+                blocksize=self._config.block_size,
+                channels=1,
+                callback=self._audio_callback,
+            )
+            self._stream.start()
+            atexit.register(self.stop)
+            return True
+        except Exception:
+            return False
+
+    def stop(self) -> None:
+        """Stop the microphone stream."""
+        if self._stream:
+            try:
+                self._stream.stop()
+                self._stream.close()
+            except Exception:
+                pass
+            self._stream = None
+
+    def _audio_callback(
+        self, indata: np.ndarray, frames: int, time_info: Any, status: Any
+    ) -> None:
+        """Process audio data from sounddevice."""
+        if not _HAS_AUDIO or np is None:
+            return
+
+        rms = np.sqrt(np.mean(indata**2))
+        if rms > 0:
+            db = 20 * np.log10(rms)
+        else:
+            db = -99.0
+
+        self._db = db
+
+        excess = max(0.0, db - self._config.threshold_db)
+        event = MicLevelEvent(
+            db_level=db, excess_above_threshold=excess, timestamp=datetime.now()
+        )
+        self._emit(event)
+
+    def _emit(self, event: MicLevelEvent) -> None:
+        """Emit event to all subscribers."""
+        for callback in self._subscribers:
+            try:
+                callback(event)
+            except Exception:
+                pass
+
+    def subscribe(self, callback: Callable[[MicLevelEvent], None]) -> None:
+        """Subscribe to mic level events."""
+        if callback not in self._subscribers:
+            self._subscribers.append(callback)
+
+    def unsubscribe(self, callback: Callable[[MicLevelEvent], None]) -> None:
+        """Unsubscribe from mic level events."""
+        if callback in self._subscribers:
+            self._subscribers.remove(callback)
+
+    def read(self) -> SensorValue | None:
+        """Read current mic level as sensor value."""
+        if not self.available:
+            return None
+
+        excess = max(0.0, self._db - self._config.threshold_db)
+        return SensorValue(
+            sensor_name=self.name,
+            value=excess,
+            timestamp=time.time(),
+            unit=self.unit,
+        )
+
+
+def register_mic_sensor() -> None:
+    """Register the mic sensor with the global registry."""
+    sensor = MicSensor()
+    SensorRegistry.register(sensor)
+
+
+# Auto-register when imported
+register_mic_sensor()

engine/sensors/oscillator.py

@@ -0,0 +1,161 @@
+"""
+Oscillator sensor - Modular synth-style oscillator as a pipeline sensor.
+
+Provides various waveforms that can be:
+1. Self-driving (phase accumulates over time)
+2. Sensor-driven (phase modulated by external sensor)
+
+Built-in waveforms:
+- sine: Pure sine wave
+- square: Square wave (0 to 1)
+- sawtooth: Rising sawtooth (0 to 1, wraps)
+- triangle: Triangle wave (0 to 1 to 0)
+- noise: Random values (0 to 1)
+
+Example usage:
+    osc = OscillatorSensor(waveform="sine", frequency=0.5)
+    # Or driven by mic sensor:
+    osc = OscillatorSensor(waveform="sine", frequency=1.0, input_sensor="mic")
+"""
+
+import math
+import random
+import time
+from enum import Enum
+
+from engine.sensors import Sensor, SensorRegistry, SensorValue
+
+
+class Waveform(Enum):
+    """Built-in oscillator waveforms."""
+
+    SINE = "sine"
+    SQUARE = "square"
+    SAWTOOTH = "sawtooth"
+    TRIANGLE = "triangle"
+    NOISE = "noise"
+
+
+class OscillatorSensor(Sensor):
+    """Oscillator sensor that generates periodic or random values.
+
+    Can run in two modes:
+    - Self-driving: phase accumulates based on frequency
+    - Sensor-driven: phase modulated by external sensor value
+    """
+
+    WAVEFORMS = {
+        "sine": lambda p: (math.sin(2 * math.pi * p) + 1) / 2,
+        "square": lambda p: 1.0 if (p % 1.0) < 0.5 else 0.0,
+        "sawtooth": lambda p: p % 1.0,
+        "triangle": lambda p: 2 * abs(2 * (p % 1.0) - 1) - 1,
+        "noise": lambda _: random.random(),
+    }
+
+    def __init__(
+        self,
+        name: str = "osc",
+        waveform: str = "sine",
+        frequency: float = 1.0,
+        input_sensor: str | None = None,
+        input_scale: float = 1.0,
+    ):
+        """Initialize oscillator sensor.
+
+        Args:
+            name: Sensor name
+            waveform: Waveform type (sine, square, sawtooth, triangle, noise)
+            frequency: Frequency in Hz (self-driving mode)
+            input_sensor: Optional sensor name to drive phase
+            input_scale: Scale factor for input sensor
+        """
+        self.name = name
+        self.unit = ""
+        self._waveform = waveform
+        self._frequency = frequency
+        self._input_sensor = input_sensor
+        self._input_scale = input_scale
+        self._phase = 0.0
+        self._start_time = time.time()
+
+    @property
+    def available(self) -> bool:
+        return True
+
+    @property
+    def waveform(self) -> str:
+        return self._waveform
+
+    @waveform.setter
+    def waveform(self, value: str) -> None:
+        if value not in self.WAVEFORMS:
+            raise ValueError(f"Unknown waveform: {value}")
+        self._waveform = value
+
+    @property
+    def frequency(self) -> float:
+        return self._frequency
+
+    @frequency.setter
+    def frequency(self, value: float) -> None:
+        self._frequency = max(0.0, value)
+
+    def start(self) -> bool:
+        self._phase = 0.0
+        self._start_time = time.time()
+        return True
+
+    def stop(self) -> None:
+        pass
+
+    def _get_input_value(self) -> float:
+        """Get value from input sensor if configured."""
+        if self._input_sensor:
+            from engine.sensors import SensorRegistry
+
+            sensor = SensorRegistry.get(self._input_sensor)
+            if sensor:
+                reading = sensor.read()
+                if reading:
+                    return reading.value * self._input_scale
+        return 0.0
+
+    def read(self) -> SensorValue | None:
+        current_time = time.time()
+        elapsed = current_time - self._start_time
+
+        if self._input_sensor:
+            input_val = self._get_input_value()
+            phase_increment = (self._frequency * elapsed) + input_val
+        else:
+            phase_increment = self._frequency * elapsed
+
+        self._phase += phase_increment
+
+        waveform_fn = self.WAVEFORMS.get(self._waveform)
+        if waveform_fn is None:
+            return None
+
+        value = waveform_fn(self._phase)
+        value = max(0.0, min(1.0, value))
+
+        return SensorValue(
+            sensor_name=self.name,
+            value=value,
+            timestamp=current_time,
+            unit=self.unit,
+        )
+
+    def set_waveform(self, waveform: str) -> None:
+        """Change waveform at runtime."""
+        self.waveform = waveform
+
+    def set_frequency(self, frequency: float) -> None:
+        """Change frequency at runtime."""
+        self.frequency = frequency
+
+
+def register_oscillator_sensor(name: str = "osc", **kwargs) -> None:
+    """Register an oscillator sensor with the global registry."""
+    sensor = OscillatorSensor(name=name, **kwargs)
+    SensorRegistry.register(sensor)

tests/test_sensors.py

@@ -0,0 +1,473 @@
+"""
+Tests for the sensor framework.
+"""
+
+import time
+
+from engine.sensors import Sensor, SensorRegistry, SensorStage, SensorValue
+
+
+class TestSensorValue:
+    """Tests for SensorValue dataclass."""
+
+    def test_create_sensor_value(self):
+        """SensorValue stores sensor data correctly."""
+        value = SensorValue(
+            sensor_name="mic",
+            value=42.5,
+            timestamp=1234567890.0,
+            unit="dB",
+        )
+
+        assert value.sensor_name == "mic"
+        assert value.value == 42.5
+        assert value.timestamp == 1234567890.0
+        assert value.unit == "dB"
+
+
+class DummySensor(Sensor):
+    """Dummy sensor for testing."""
+
+    def __init__(self, name: str = "dummy", value: float = 1.0):
+        self.name = name
+        self.unit = "units"
+        self._value = value
+
+    def start(self) -> bool:
+        return True
+
+    def stop(self) -> None:
+        pass
+
+    def read(self) -> SensorValue | None:
+        return SensorValue(
+            sensor_name=self.name,
+            value=self._value,
+            timestamp=time.time(),
+            unit=self.unit,
+        )
+
+
+class TestSensorRegistry:
+    """Tests for SensorRegistry."""
+
+    def setup_method(self):
+        """Clear registry before each test."""
+        SensorRegistry._sensors.clear()
+        SensorRegistry._started = False
+
+    def test_register_sensor(self):
+        """SensorRegistry registers sensors."""
+        sensor = DummySensor()
+        SensorRegistry.register(sensor)
+
+        assert SensorRegistry.get("dummy") is sensor
+
+    def test_list_sensors(self):
+        """SensorRegistry lists registered sensors."""
+        SensorRegistry.register(DummySensor("a"))
+        SensorRegistry.register(DummySensor("b"))
+
+        sensors = SensorRegistry.list_sensors()
+        assert "a" in sensors
+        assert "b" in sensors
+
+    def test_read_all(self):
+        """SensorRegistry reads all sensor values."""
+        SensorRegistry.register(DummySensor("a", 1.0))
+        SensorRegistry.register(DummySensor("b", 2.0))
+
+        values = SensorRegistry.read_all()
+        assert values["a"] == 1.0
+        assert values["b"] == 2.0
+
+
+class TestSensorStage:
+    """Tests for SensorStage pipeline adapter."""
+
+    def setup_method(self):
+        SensorRegistry._sensors.clear()
+        SensorRegistry._started = False
+
+    def test_sensor_stage_capabilities(self):
+        """SensorStage declares correct capabilities."""
+        sensor = DummySensor("mic")
+        stage = SensorStage(sensor)
+
+        assert "sensor.mic" in stage.capabilities
+
+    def test_sensor_stage_process(self):
+        """SensorStage reads sensor and stores in context."""
+        from engine.pipeline.core import PipelineContext
+
+        sensor = DummySensor("test", 42.0)
+        stage = SensorStage(sensor, "test")
+
+        ctx = PipelineContext()
+        result = stage.process(None, ctx)
+
+        assert ctx.get_state("sensor.test") == 42.0
+        assert result is None
+
+
+class TestApplyParamBindings:
+    """Tests for sensor param bindings."""
+
+    def test_no_bindings_returns_original(self):
+        """Effect without bindings returns original config."""
+        from engine.effects.types import (
+            EffectConfig,
+            EffectPlugin,
+            apply_param_bindings,
+        )
+
+        class TestEffect(EffectPlugin):
+            name = "test"
+            config = EffectConfig()
+
+            def process(self, buf, ctx):
+                return buf
+
+            def configure(self, config):
+                pass
+
+        effect = TestEffect()
+        ctx = object()
+
+        result = apply_param_bindings(effect, ctx)
+        assert result is effect.config
+
+    def test_bindings_read_sensor_values(self):
+        """Param bindings read sensor values from context."""
+        from engine.effects.types import (
+            EffectConfig,
+            EffectPlugin,
+            apply_param_bindings,
+        )
+
+        class TestEffect(EffectPlugin):
+            name = "test"
+            config = EffectConfig(intensity=1.0)
+            param_bindings = {
+                "intensity": {"sensor": "mic", "transform": "linear"},
+            }
+
+            def process(self, buf, ctx):
+                return buf
+
+            def configure(self, config):
+                pass
+
+        from engine.effects.types import EffectContext
+
+        effect = TestEffect()
+        ctx = EffectContext(
+            terminal_width=80,
+            terminal_height=24,
+            scroll_cam=0,
+            ticker_height=20,
+        )
+        ctx.set_state("sensor.mic", 0.8)
+
+        result = apply_param_bindings(effect, ctx)
+        assert "intensity_sensor" in result.params
+
+
+class TestSensorLifecycle:
+    """Tests for sensor start/stop lifecycle."""
+
+    def setup_method(self):
+        SensorRegistry._sensors.clear()
+        SensorRegistry._started = False
+
+    def test_start_all(self):
+        """SensorRegistry starts all sensors."""
+        started = []
+
+        class StatefulSensor(Sensor):
+            name = "stateful"
+
+            def start(self) -> bool:
+                started.append("start")
+                return True
+
+            def stop(self) -> None:
+                started.append("stop")
+
+            def read(self) -> SensorValue | None:
+                return SensorValue("stateful", 1.0, 0.0)
+
+        SensorRegistry.register(StatefulSensor())
+        SensorRegistry.start_all()
+
+        assert "start" in started
+        assert SensorRegistry._started is True
+
+    def test_stop_all(self):
+        """SensorRegistry stops all sensors."""
+        stopped = []
+
+        class StatefulSensor(Sensor):
+            name = "stateful"
+
+            def start(self) -> bool:
+                return True
+
+            def stop(self) -> None:
+                stopped.append("stop")
+
+            def read(self) -> SensorValue | None:
+                return SensorValue("stateful", 1.0, 0.0)
+
+        SensorRegistry.register(StatefulSensor())
+        SensorRegistry.start_all()
+        SensorRegistry.stop_all()
+
+        assert "stop" in stopped
+        assert SensorRegistry._started is False
+
+    def test_unavailable_sensor(self):
+        """Unavailable sensor returns None from read."""
+
+        class UnavailableSensor(Sensor):
+            name = "unavailable"
+
+            @property
+            def available(self) -> bool:
+                return False
+
+            def start(self) -> bool:
+                return False
+
+            def stop(self) -> None:
+                pass
+
+            def read(self) -> SensorValue | None:
+                return None
+
+        sensor = UnavailableSensor()
+        assert sensor.available is False
+        assert sensor.read() is None
+
+
+class TestTransforms:
+    """Tests for sensor value transforms."""
+
+    def test_exponential_transform(self):
+        """Exponential transform squares the value."""
+        from engine.effects.types import (
+            EffectConfig,
+            EffectPlugin,
+            apply_param_bindings,
+        )
+
+        class TestEffect(EffectPlugin):
+            name = "test"
+            config = EffectConfig(intensity=1.0)
+            param_bindings = {
+                "intensity": {"sensor": "mic", "transform": "exponential"},
+            }
+
+            def process(self, buf, ctx):
+                return buf
+
+            def configure(self, config):
+                pass
+
+        from engine.effects.types import EffectContext
+
+        effect = TestEffect()
+        ctx = EffectContext(80, 24, 0, 20)
+        ctx.set_state("sensor.mic", 0.5)
+
+        result = apply_param_bindings(effect, ctx)
+        # 0.5^2 = 0.25, then scaled: 0.5 + 0.25*0.5 = 0.625
+        assert result.intensity != effect.config.intensity
+
+    def test_inverse_transform(self):
+        """Inverse transform inverts the value."""
+        from engine.effects.types import (
+            EffectConfig,
+            EffectPlugin,
+            apply_param_bindings,
+        )
+
+        class TestEffect(EffectPlugin):
+            name = "test"
+            config = EffectConfig(intensity=1.0)
+            param_bindings = {
+                "intensity": {"sensor": "mic", "transform": "inverse"},
+            }
+
+            def process(self, buf, ctx):
+                return buf
+
+            def configure(self, config):
+                pass
+
+        from engine.effects.types import EffectContext
+
+        effect = TestEffect()
+        ctx = EffectContext(80, 24, 0, 20)
+        ctx.set_state("sensor.mic", 0.8)
+
+        result = apply_param_bindings(effect, ctx)
+        # 1.0 - 0.8 = 0.2
+        assert abs(result.params["intensity_sensor"] - 0.2) < 0.001
+
+    def test_threshold_transform(self):
+        """Threshold transform applies binary threshold."""
+        from engine.effects.types import (
+            EffectConfig,
+            EffectPlugin,
+            apply_param_bindings,
+        )
+
+        class TestEffect(EffectPlugin):
+            name = "test"
+            config = EffectConfig(intensity=1.0)
+            param_bindings = {
+                "intensity": {
+                    "sensor": "mic",
+                    "transform": "threshold",
+                    "threshold": 0.5,
+                },
+            }
+
+            def process(self, buf, ctx):
+                return buf
+
+            def configure(self, config):
+                pass
+
+        from engine.effects.types import EffectContext
+
+        effect = TestEffect()
+        ctx = EffectContext(80, 24, 0, 20)
+
+        # Above threshold
+        ctx.set_state("sensor.mic", 0.8)
+        result = apply_param_bindings(effect, ctx)
+        assert result.params["intensity_sensor"] == 1.0
+
+        # Below threshold
+        ctx.set_state("sensor.mic", 0.3)
+        result = apply_param_bindings(effect, ctx)
+        assert result.params["intensity_sensor"] == 0.0
+
+
+class TestOscillatorSensor:
+    """Tests for OscillatorSensor."""
+
+    def setup_method(self):
+        SensorRegistry._sensors.clear()
+        SensorRegistry._started = False
+
+    def test_sine_waveform(self):
+        """Oscillator generates sine wave."""
+        from engine.sensors.oscillator import OscillatorSensor
+
+        osc = OscillatorSensor(name="test", waveform="sine", frequency=1.0)
+        osc.start()
+
+        values = [osc.read().value for _ in range(10)]
+        assert all(0 <= v <= 1 for v in values)
+
+    def test_square_waveform(self):
+        """Oscillator generates square wave."""
+        from engine.sensors.oscillator import OscillatorSensor
+
+        osc = OscillatorSensor(name="test", waveform="square", frequency=10.0)
+        osc.start()
+
+        values = [osc.read().value for _ in range(10)]
+        assert all(v in (0.0, 1.0) for v in values)
+
+    def test_waveform_types(self):
+        """All waveform types work."""
+        from engine.sensors.oscillator import OscillatorSensor
+
+        for wf in ["sine", "square", "sawtooth", "triangle", "noise"]:
+            osc = OscillatorSensor(name=wf, waveform=wf, frequency=1.0)
+            osc.start()
+            val = osc.read()
+            assert val is not None
+            assert 0 <= val.value <= 1
+
+    def test_invalid_waveform_raises(self):
+        """Invalid waveform returns None."""
+        from engine.sensors.oscillator import OscillatorSensor
+
+        osc = OscillatorSensor(waveform="invalid")
+        osc.start()
+        val = osc.read()
+        assert val is None
+
+    def test_sensor_driven_oscillator(self):
+        """Oscillator can be driven by another sensor."""
+        from engine.sensors.oscillator import OscillatorSensor
+
+        class ModSensor(Sensor):
+            name = "mod"
+
+            def start(self) -> bool:
+                return True
+
+            def stop(self) -> None:
+                pass
+
+            def read(self) -> SensorValue | None:
+                return SensorValue("mod", 0.5, 0.0)
+
+        SensorRegistry.register(ModSensor())
+
+        osc = OscillatorSensor(
+            name="lfo", waveform="sine", frequency=0.1, input_sensor="mod"
+        )
+        osc.start()
+
+        val = osc.read()
+        assert val is not None
+        assert 0 <= val.value <= 1
+
+
+class TestMicSensor:
+    """Tests for MicSensor."""
+
+    def setup_method(self):
+        SensorRegistry._sensors.clear()
+        SensorRegistry._started = False
+
+    def test_mic_sensor_creation(self):
+        """MicSensor can be created."""
+        from engine.sensors.mic import MicSensor
+
+        sensor = MicSensor()
+        assert sensor.name == "mic"
+        assert sensor.unit == "dB"
+
+    def test_mic_sensor_custom_name(self):
+        """MicSensor can have custom name."""
+        from engine.sensors.mic import MicSensor
+
+        sensor = MicSensor(name="my_mic")
+        assert sensor.name == "my_mic"
+
+    def test_mic_sensor_start(self):
+        """MicSensor.start returns bool."""
+        from engine.sensors.mic import MicSensor
+
+        sensor = MicSensor()
+        result = sensor.start()
+        assert isinstance(result, bool)
+
+    def test_mic_sensor_read_returns_value_or_none(self):
+        """MicSensor.read returns SensorValue or None."""
+        from engine.sensors.mic import MicSensor
+
+        sensor = MicSensor()
+        sensor.start()
+        # May be None if no mic available
+        result = sensor.read()
+        # Just check it doesn't raise - result depends on system
+        assert result is None or isinstance(result, SensorValue)