feat: add YouTubeAdapter with injectable client seam

worker/tests/test_youtube_adapter.py

@@ -0,0 +1,65 @@
+from lyra_worker.adapters.youtube import YouTubeAdapter
+from lyra_worker.types import Candidate, MBTarget, Quality
+
+TARGET = MBTarget(artist="Radiohead", album="In Rainbows", track_count=10)
+
+
+class FakeYtClient:
+    def __init__(self, results=None, fail=False):
+        self._results = results if results is not None else [
+            {"source_ref": "yt:playlist:abc", "title": "In Rainbows", "artist": "Radiohead", "track_count": 10}
+        ]
+        self._fail = fail
+        self.downloaded = []
+
+    def search_album(self, artist, album):
+        return self._results
+
+    def download(self, source_ref, dest, on_progress):
+        if self._fail:
+            raise RuntimeError("network boom")
+        on_progress(1.0)
+        self.downloaded.append((source_ref, dest))
+        return {"track_count": 10, "path": dest}
+
+
+def test_name_and_tier():
+    a = YouTubeAdapter(FakeYtClient())
+    assert a.name == "youtube"
+    assert a.tier == 2
+    assert a.health() is True
+
+
+def test_search_maps_results_to_candidates():
+    cands = YouTubeAdapter(FakeYtClient()).search(TARGET)
+    assert len(cands) == 1
+    c = cands[0]
+    assert c.source == "youtube"
+    assert c.source_ref == "yt:playlist:abc"
+    assert c.matched_artist == "Radiohead"
+    assert c.matched_album == "In Rainbows"
+    assert c.track_count == 10
+    assert c.source_tier == 2
+    assert c.quality.lossless is False
+
+
+def test_search_empty_when_no_results():
+    assert YouTubeAdapter(FakeYtClient(results=[])).search(TARGET) == []
+
+
+def test_download_success():
+    client = FakeYtClient()
+    cand = YouTubeAdapter(client).search(TARGET)[0]
+    seen = []
+    result = YouTubeAdapter(client).download(cand, "/tmp/x", seen.append)
+    assert result.ok is True
+    assert result.track_count == 10
+    assert seen and seen[-1] == 1.0
+
+
+def test_download_failure_returns_not_ok():
+    client = FakeYtClient(fail=True)
+    cand = YouTubeAdapter(FakeYtClient()).search(TARGET)[0]
+    result = YouTubeAdapter(client).download(cand, "/tmp/x", lambda _p: None)
+    assert result.ok is False
+    assert result.error