Add diarization speaker-bound validation tests

tests/test_diarization_service.py

@@ -0,0 +1,20 @@
+from __future__ import annotations
+
+import pytest
+
+from app.core.exceptions import InputError
+from app.services.diarization_service import DiarizationService
+
+
+def test_speaker_bounds_validation() -> None:
+    service = DiarizationService(None)  # type: ignore[arg-type]
+    with pytest.raises(InputError, match="between 1 and 32"):
+        import asyncio
+        asyncio.run(service.diarize(__import__("pathlib").Path("/missing"), "audio/wav", "x.wav", min_speakers=0))
+
+
+def test_speaker_bounds_order_validation() -> None:
+    service = DiarizationService(None)  # type: ignore[arg-type]
+    with pytest.raises(InputError, match="cannot exceed"):
+        import asyncio
+        asyncio.run(service.diarize(__import__("pathlib").Path("/missing"), "audio/wav", "x.wav", min_speakers=4, max_speakers=2))