Retry transient TTS synthesis failures

tests/test_tts_retry.py

@@ -0,0 +1,48 @@
+"""Tests for transient Edge TTS retry behavior."""
+
+from __future__ import annotations
+
+import asyncio
+
+from src.engines import Engine
+from src.translation import TranslationConfig
+
+
+def test_synthesize_retries_transient_edge_tts_failure(tmp_path, monkeypatch):
+    calls = {"count": 0}
+
+    class FakeCommunicate:
+        def __init__(self, text, voice, rate):
+            self.text = text
+            self.voice = voice
+            self.rate = rate
+
+        async def save(self, out_path):
+            calls["count"] += 1
+            if calls["count"] == 1:
+                raise RuntimeError("transient 503")
+            with open(out_path, "wb") as audio_file:
+                audio_file.write(b"0" * 2048)
+
+    async def no_sleep(_seconds):
+        return None
+
+    monkeypatch.setattr("src.engines.edge_tts.Communicate", FakeCommunicate)
+    monkeypatch.setattr("src.engines.asyncio.sleep", no_sleep)
+    monkeypatch.setattr("src.engines.DEFAULT_TTS_MAX_RETRIES", 2)
+
+    engine = Engine(
+        "cpu",
+        translation_config=TranslationConfig(
+            base_url="http://127.0.0.1:1234/v1",
+            api_key="test-key",
+            model="test-model",
+        ),
+    )
+    out_path = tmp_path / "tts.mp3"
+
+    asyncio.run(engine.synthesize("Bonjour", "fr", out_path))
+
+    assert calls["count"] == 2
+    assert out_path.exists()
+    assert out_path.stat().st_size == 2048