diff --git a/library/library_test.go b/library/library_test.go
index c95ccfb..5a2eac4 100644
--- a/library/library_test.go
+++ b/library/library_test.go
@@ -200,3 +200,68 @@ func TestLetterName(t *testing.T) {
 		}
 	}
 }
+
+func TestCustomTagger(t *testing.T) {
+    want := trackInfo{
+        Artist: "Custom Artist",
+        Album: "Custom Album",
+        Title: "Custom Title",
+    }
+
+    tagF := func(idx int) *id3v2.Tag {
+        t := id3v2.NewEmptyTag()
+        t.SetArtist(want.Artist)
+        t.SetAlbum(want.Album)
+        t.SetTitle(want.Title)
+        return t
+    }
+
+    lib, err := New(bytes.NewReader(nil))
+    if err != nil {
+        t.Fatalf("Failed to create new library: %v", err)
+    }
+    lib.Tagger = tagF
+
+    gotSong, err := lib.SongAt(0) 
+    if err != nil {
+        t.Fatalf("lib.SongAt(0) = %v", err)
+    }
+    got, err := songInfo(gotSong)
+    if err != nil {
+        t.Fatalf("songInfo(...) = _, %v, want _, nil", err)
+    }
+
+    if diff := cmp.Diff(want, got); diff != "" {
+        t.Errorf("lib.SongAt(0) had unexpected diff (want -> got):\n%s", diff)
+    }
+}
+
+func TestCustomPather(t *testing.T) {
+    wantTag := id3v2.NewEmptyTag()
+    const want = "abc.mp3" 
+
+    lib, err := New(bytes.NewReader(nil))
+    if err != nil {
+        t.Fatalf("Failed to create new library: %v", err)
+    }
+    lib.Tagger = func(int) *id3v2.Tag {
+        return wantTag 
+    }
+    lib.Pather = func(_ int, gotTag *id3v2.Tag) string {
+        // Need to make sure that the pather is passed the tag from the
+        // tagger.
+        if wantTag != gotTag {
+            t.Errorf("Pather got unexpected tag %v, want %v", gotTag, wantTag)
+        }
+        return want
+    }
+
+    got, err := lib.PathAt(0)
+    if err != nil {
+        t.Fatalf("lib.PathAt(0) = _, %v; want _, nil", err)
+    }
+
+    if got != want {
+        t.Errorf("lib.PathAt(0) = %q, want %q", got, want)
+    }
+}