'Test the _write_cell() method for strings.'

def test_write_cell_string(self):

    cell_tuple = namedtuple('String', 'string,    format')
    cell = cell_tuple(0, None)
    self.worksheet._write_cell(3, 1, cell)
    exp = '<c    r="B4"    t="s"><v>0</v></c>'
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
