'Test the _write_mru_colors() method'

def test_write_mru_colors(self):

    self.styles._write_mru_colors(['FF26DA55', 'FF792DC8', 'FF646462'])
    exp = '<mruColors><color    rgb="FF646462"/><color    rgb="FF792DC8"/><color    rgb="FF26DA55"/></mruColors>'
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
