def METHOD_NAME(self):
    format_tags = self.mod.main.format_tags
    def getline(key, value):
        song = AudioFile({"~filename": fsnative(u"/dev/null")})
        song.sanitize()
        song[key] = value
        lines = format_tags(song).splitlines()
        if not lines:
            return ""
        if len(lines) == 1:
            return lines[0]
        # hackery since title defaults to the filename..
        for l in lines:
            if not l.startswith("Title"):
                return l
    self.assertEqual(getline("artist", "foo"), "Artist: foo")
    self.assertEqual(getline("genre", "foo\nbar"), "Genre: foo, bar")
    self.assertEqual(getline("artistsort", "foo"), "ArtistSort: foo")
    self.assertEqual(getline("tracknumber", "2/3"), "Track: 2/3")
    self.assertEqual(getline("discnumber", "2/3"), "Disc: 2/3")
    self.assertEqual(getline("date", "2009-03-04"), "Date: 2009")