changes

crates/domain/tests/song/song_test.rs

@@ -0,0 +1,44 @@
+use domain::song::{RecordingId, Song};
+
+#[test]
+fn a_song_needs_only_a_title_and_an_artist() {
+    let song = Song::new("Paranoid Android", "Radiohead", None, None).unwrap();
+
+    assert_eq!(song.title().value(), "Paranoid Android");
+    assert_eq!(song.artist().value(), "Radiohead");
+    assert!(song.album().is_none());
+    assert!(song.recording_id().is_none());
+}
+
+#[test]
+fn a_song_records_its_album_and_external_identity_when_known() {
+    let recording = RecordingId::new("f5c7e7a2-0000-4000-8000-000000000001").unwrap();
+    let song = Song::new(
+        "Paranoid Android",
+        "Radiohead",
+        Some("OK Computer".into()),
+        Some(recording),
+    )
+    .unwrap();
+
+    assert_eq!(song.album().map(|a| a.value()), Some("OK Computer"));
+    assert!(song.recording_id().is_some());
+}
+
+#[test]
+fn a_song_without_a_title_or_artist_is_rejected() {
+    assert!(Song::new("", "Radiohead", None, None).is_err());
+    assert!(Song::new("Paranoid Android", "   ", None, None).is_err());
+}
+
+#[test]
+fn a_recording_id_that_is_not_a_uuid_is_rejected() {
+    assert!(RecordingId::new("not-a-musicbrainz-id").is_err());
+}
+
+#[test]
+fn a_blank_album_is_treated_as_absent() {
+    let song = Song::new("Airbag", "Radiohead", Some("   ".into()), None).unwrap();
+
+    assert!(song.album().is_none());
+}