'Test the _write_sheet_pr() method'

def test_write_sheet_pr_tab_color(self):

    self.worksheet.set_tab_color('red')
    self.worksheet._write_sheet_pr()
    exp = '<sheetPr><tabColor    rgb="FFFF0000"/></sheetPr>'
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
