[DEV] Unit test music tags (#1074)

tests/unit/plugins/test_music_tags.py

@@ -0,0 +1,48 @@
+import re
+
+import pytest
+
+from ytdl_sub.subscriptions.subscription import Subscription
+from ytdl_sub.utils.exceptions import ValidationException
+
+
+@pytest.fixture
+def single_song_video_dict(output_directory):
+    return {
+        "download": "https://your.name.here",
+        "output_options": {"output_directory": output_directory, "file_name": "will_error.mp4"},
+        # test multi-tags compile
+        "music_tags": {"genres": ["multi_tag_1", "multi_tag_2"]},
+    }
+
+
+class TestMusicTags:
+    def test_music_tags_errors_on_video(
+        self,
+        config,
+        single_song_video_dict,
+        output_directory,
+        subscription_name,
+        mock_download_collection_entries,
+    ):
+        subscription = Subscription.from_dict(
+            config=config,
+            preset_name=subscription_name,
+            preset_dict=single_song_video_dict,
+        )
+
+        with (
+            mock_download_collection_entries(
+                is_youtube_channel=False, num_urls=1, is_extracted_audio=False, is_dry_run=True
+            ),
+            pytest.raises(
+                ValidationException,
+                match=re.escape(
+                    f"Validation error in {subscription_name}.music_tags: music_tags plugin received a "
+                    "video with the extension 'mp4'. Only audio files are supported for setting music "
+                    "tags. Ensure you are converting the video to audio using the audio_extract "
+                    "plugin."
+                ),
+            ),
+        ):
+            subscription.download(dry_run=True)