Add tests for watch_status pure functions and early exits

This adds `tests/test_watch_status.py` to cover the `_artist_variants`
pure function and the non-DB paths of `music_listening_stats`
(early exit and DB exception handling) adhering to the test runner
conventions.

Co-authored-by: Randomname653 <127677734+Randomname653@users.noreply.github.com>

Author: google-labs-jules[bot]

tests/test_watch_status.py

@@ -0,0 +1,52 @@
+from unittest.mock import patch
+
+from src.services.watch_status import _artist_variants, music_listening_stats
+
+def test_artist_variants():
+    # Empty inputs
+    assert _artist_variants(None) == [""]
+    assert _artist_variants("") == [""]
+    assert _artist_variants("   ") == [""]
+
+    # Normal base case
+    assert sorted(_artist_variants("Artist")) == ["artist"]
+
+    # Dash folding test for every dash in _DASHES
+    # The dashes are: "‐‑‒–—−"
+    dashes = "‐‑‒–—−"
+    for dash in dashes:
+        # Each dash variant should produce a set containing the lowercase dash variant AND the folded dash variant
+        name = f"Jay{dash}Z"
+        variants = _artist_variants(name)
+        assert len(variants) == 2, f"Expected 2 variants for dash '{dash}', got {variants}"
+        assert "jay-z" in variants, f"Expected 'jay-z' in variants for dash '{dash}', got {variants}"
+        assert name.lower() in variants, f"Expected '{name.lower()}' in variants for dash '{dash}', got {variants}"
+
+def test_music_listening_stats_early_exit():
+    # Test early exit conditions (returns None before DB access)
+
+    # Missing user_id
+    assert music_listening_stats(0, "Artist") is None
+    assert music_listening_stats(None, "Artist") is None
+
+    # Missing both artist and artist_mbid
+    assert music_listening_stats(1, "") is None
+    assert music_listening_stats(1, None) is None
+    assert music_listening_stats(1, "", "") is None
+
+    # With user_id and one of artist/mbid, it proceeds past early exit
+    # (Since we haven't mocked DB here, if we pass valid args it will try to access DB,
+    # but for early exit we just test the None returns).
+
+def test_music_listening_stats_exception():
+    # Test that DB exceptions are caught and return None
+    import contextlib
+
+    @contextlib.contextmanager
+    def mock_get_db_session():
+        raise Exception("Mock DB connection failure")
+        yield # just to make it a generator for context manager
+
+    with patch("src.database.connection.get_db_session", new=mock_get_db_session):
+        result = music_listening_stats(1, "Artist")
+        assert result is None