'Test the _write_font() method. Default properties.'

def test_write_font_1(self):

    properties = {}
    xf_format = Format(properties)
    self.styles._write_font(xf_format)
    exp = '<font><sz    val="11"/><color    theme="1"/><name    val="Calibri"/><family    val="2"/><scheme    val="minor"/></font>'
    got = self.fh.getvalue()
    self.assertEqual(got, exp)
