def METHOD_NAME(self):
    """Test the _write_font() method. Underline."""
    properties = {"underline": 1}
    xf_format = Format(properties)
    self.styles._write_font(xf_format)
    exp = """<font><u/><sz val="11"/><color theme="1"/><name val="Calibri"/><family val="2"/><scheme val="minor"/></font>"""
    got = self.fh.getvalue()
    self.assertEqual(got, exp)