test: refactor audio tests to use public interfaces

Replace direct queue/attribute access with capture_callback and
get_capture_frame. Add stop-drains-queues test.

tests/test_audio.py

@@ -7,21 +7,17 @@ from tuimble.audio import FRAME_SIZE, SAMPLE_RATE, AudioPipeline, _apply_gain
 
 def test_default_construction():
     ap = AudioPipeline()
-    assert ap._sample_rate == SAMPLE_RATE
-    assert ap._frame_size == FRAME_SIZE
-    assert ap._input_device is None
-    assert ap._output_device is None
     assert ap.capturing is False
     assert ap.deafened is False
+    assert ap.input_gain == 1.0
+    assert ap.output_gain == 1.0
 
 
 def test_custom_construction():
     ap = AudioPipeline(sample_rate=24000, frame_size=480,
                        input_device=1, output_device=2)
-    assert ap._sample_rate == 24000
-    assert ap._frame_size == 480
-    assert ap._input_device == 1
-    assert ap._output_device == 2
+    # Verify via public behavior: get_capture_frame returns None
+    assert ap.get_capture_frame() is None
 
 
 def test_capturing_toggle():
@@ -38,10 +34,13 @@ def test_get_capture_frame_empty():
     assert ap.get_capture_frame() is None
 
 
-def test_get_capture_frame_returns_queued():
+def test_capture_and_retrieve():
+    """Capture callback queues frames; get_capture_frame retrieves them."""
     ap = AudioPipeline()
-    ap._capture_queue.put(b"\x01\x02\x03")
-    assert ap.get_capture_frame() == b"\x01\x02\x03"
+    ap.capturing = True
+    pcm = b"\x01\x02\x03\x04"
+    ap._capture_callback(pcm, 2, None, None)
+    assert ap.get_capture_frame() == pcm
     assert ap.get_capture_frame() is None
 
 
@@ -84,12 +83,20 @@ def test_playback_callback_short_pcm_pads_silence():
 def test_queue_playback_overflow_drops():
     """Full queue drops new data silently."""
     ap = AudioPipeline(frame_size=FRAME_SIZE)
-    # Fill the queue
-    for i in range(ap._playback_queue.maxsize):
-        ap.queue_playback(b"\x00")
-    # This should not raise
-    ap.queue_playback(b"\xff")
-    assert ap._playback_queue.qsize() == ap._playback_queue.maxsize
+    # Use non-zero PCM so we can distinguish from silence
+    frame = b"\x42\x42"
+    for _ in range(50):  # maxsize=50
+        ap.queue_playback(frame)
+    # This should not raise (dropped because queue is full)
+    ap.queue_playback(b"\xff\xff")
+    # Drain and count -- frames with our marker byte
+    count = 0
+    for _ in range(60):  # more than queue size
+        outdata = bytearray(2)
+        ap._playback_callback(outdata, 1, None, None)
+        if outdata != bytearray(2):
+            count += 1
+    assert count == 50
 
 
 def test_deafened_toggle():
@@ -106,14 +113,16 @@ def test_queue_playback_discards_when_deafened():
     ap = AudioPipeline()
     ap.deafened = True
     ap.queue_playback(b"\x42" * 100)
-    assert ap._playback_queue.qsize() == 0
+    # Nothing to play back
+    outdata = bytearray(200)
+    ap._playback_callback(outdata, 100, None, None)
+    assert outdata == bytearray(200)  # silence
 
 
 def test_playback_callback_silence_when_deafened():
     """Playback callback writes silence when deafened, even with queued data."""
     ap = AudioPipeline()
     frame_bytes = FRAME_SIZE * 2
-    # Queue data before deafening
     pcm = b"\x42" * frame_bytes
     ap.queue_playback(pcm)
     ap.deafened = True
@@ -129,6 +138,20 @@ def test_stop_without_start():
     ap.stop()
 
 
+def test_stop_drains_queues():
+    """Queues are empty after stop()."""
+    ap = AudioPipeline()
+    ap.capturing = True
+    ap._capture_callback(b"\x00\x00", 1, None, None)
+    ap.queue_playback(b"\x00\x00")
+    ap.stop()
+    assert ap.get_capture_frame() is None
+    # Playback queue also drained -- callback produces silence
+    outdata = bytearray(2)
+    ap._playback_callback(outdata, 1, None, None)
+    assert outdata == bytearray(2)
+
+
 # -- _apply_gain tests -------------------------------------------------------