added basic tests

internal/data/song.go

@@ -105,6 +105,7 @@ func (m Song) Merge(other MusicObject) MusicObject {
 func (m Song) Compile() MusicObject {
 	m.Sources = dedupeSources(m.Sources)
 	m.UnifiedName = common.Unify(m.Name)
+	m.Album = m.Album.Compile().(Album)
 	m.Artists = dedupeMusicObjects(m.Artists)
 	return m
 }

internal/data/song_test.go

@@ -0,0 +1,34 @@
+package data
+
+import (
+	"testing"
+)
+
+func TestSong(t *testing.T) {
+	song := Song{
+		Name: "song_a",
+		Album: Album{
+			Name: "album_a",
+			Artists: []Artist{
+				{Name: "artist_a"},
+				{Name: "artist_a"},
+				{Name: "artist_b"},
+			},
+		},
+		Artists: []Artist{
+			{Name: "artist_a"},
+			{Name: "artist_a"},
+			{Name: "artist_b"},
+		},
+	}
+
+	compiled := song.Compile().(Song)
+
+	if len(compiled.Artists) != 2 {
+		t.Errorf(`the two artists with the same name have to be merged, %d`, len(compiled.Artists))
+	}
+
+	if len(compiled.Album.Artists) != 2 {
+		t.Errorf(`the two artists with the same names in the album have to be merged, %d`, len(compiled.Album.Artists))
+	}
+}