def test_update_artists(self): artist = Artist('my_artist_name') artist.add_track('my_track_name', '10/01/01') artist.add_track('my_second_track_name', '10/01/01') artist2 = Artist('my_artist_name') artist2.add_track('my_track_name', '11/01/01') artist2.add_track('my_second_track_name', '11/01/01') #This one will not be added because it is the same date artist2.add_track('my_track_name', '11/01/01') artist.update(artist2) self.assertEqual(len(artist), 4) artist3 = Artist('my_other_artist_name') artist3.add_track('my_track_name', '11/01/01') self.assertRaises(AttributeError, artist.update, artist3) self.assertEqual(len(artist), 4)