'Test the _write_auto_filter() method'

def test_write_auto_filter_21(self):

    matches = ['February', 'January', 'July', 'June']
    exp = '<autoFilter    ref="A1:D51"><filterColumn    colId="3"><filters><filter    val="February"/><filter    val="January"/><filter    val="July"/><filter    val="June"/></filters></filterColumn></autoFilter>'
    self.worksheet.filter_column_list(3, matches)
    self.worksheet._write_auto_filter()
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
