Fail fast when configured recording input cannot be resolved

tests/test_recorder.py

@@ -3,12 +3,14 @@ import unittest
 from pathlib import Path
 
 import numpy as np
+from unittest.mock import patch
 
 ROOT = Path(__file__).resolve().parents[1]
 SRC = ROOT / "src"
 if str(SRC) not in sys.path:
     sys.path.insert(0, str(SRC))
 
+import recorder
 from recorder import RecordResult, stop_recording
 
 
@@ -30,6 +32,40 @@ class _Stream:
             raise self.close_exc
 
 
+class _InputStream:
+    def __init__(self, **kwargs):
+        self.kwargs = kwargs
+        self.started = False
+
+    def start(self) -> None:
+        self.started = True
+
+    def stop(self) -> None:
+        return
+
+    def close(self) -> None:
+        return
+
+
+class _FakeSoundDevice:
+    def __init__(self):
+        self.default = type("Default", (), {"device": (0, None)})()
+        self.created_streams = []
+        self._devices = [
+            {"name": "Built-in Output", "max_input_channels": 0},
+            {"name": "Laptop Mic", "max_input_channels": 1},
+            {"name": "USB Interface", "max_input_channels": 2},
+        ]
+
+    def query_devices(self):
+        return self._devices
+
+    def InputStream(self, **kwargs):
+        stream = _InputStream(**kwargs)
+        self.created_streams.append(stream)
+        return stream
+
+
 class RecorderTests(unittest.TestCase):
     def test_stop_recording_closes_stream_when_stop_raises(self):
         stream = _Stream(stop_exc=RuntimeError("stop boom"))
@@ -75,6 +111,40 @@ class RecorderTests(unittest.TestCase):
 
         np.testing.assert_allclose(audio, np.array([0.2, 0.4], dtype=np.float32))
 
+    def test_start_recording_accepts_explicit_device_name(self):
+        sd = _FakeSoundDevice()
+        with patch("recorder._sounddevice", return_value=sd):
+            stream, record = recorder.start_recording("Laptop")
+
+        self.assertTrue(stream.started)
+        self.assertEqual(stream.kwargs["device"], 1)
+        self.assertEqual(record.channels, 1)
+
+    def test_start_recording_accepts_explicit_device_index(self):
+        sd = _FakeSoundDevice()
+        with patch("recorder._sounddevice", return_value=sd):
+            stream, _record = recorder.start_recording(2)
+
+        self.assertTrue(stream.started)
+        self.assertEqual(stream.kwargs["device"], 2)
+
+    def test_start_recording_invalid_explicit_name_raises(self):
+        sd = _FakeSoundDevice()
+        with patch("recorder._sounddevice", return_value=sd):
+            with self.assertRaisesRegex(
+                ValueError,
+                "did not match any input device; available inputs: 1:Laptop Mic, 2:USB Interface",
+            ):
+                recorder.start_recording("NotADevice")
+
+    def test_start_recording_empty_input_uses_default(self):
+        sd = _FakeSoundDevice()
+        with patch("recorder._sounddevice", return_value=sd):
+            stream, _record = recorder.start_recording("")
+
+        self.assertTrue(stream.started)
+        self.assertIsNone(stream.kwargs["device"])
+
 
 if __name__ == "__main__":
     unittest.main()