'Test writing a worksheet with a blank cell with write() method.'

def test_assemble_xml_file_write(self):

    self.maxDiff = None
    fh = StringIO()
    worksheet = Worksheet()
    worksheet._set_filehandle(fh)
    cell_format = Format({'xf_index': 1})
    worksheet.write(0, 0, None)
    worksheet.write(1, 2, None, cell_format)
    worksheet.select()
    worksheet._assemble_xml_file()
    exp = _xml_to_list('\n                                                                <?xml    version="1.0"    encoding="UTF-8"    standalone="yes"?>\n                                                                <worksheet    xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"    xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">\n                                                                        <dimension    ref="C2"/>\n                                                                        <sheetViews>\n                                                                                <sheetView    tabSelected="1"    workbookViewId="0"/>\n                                                                        </sheetViews>\n                                                                        <sheetFormatPr    defaultRowHeight="15"/>\n                                                                        <sheetData>\n                                                                                <row    r="2"    spans="3:3">\n                                                                                        <c    r="C2"    s="1"/>\n                                                                                </row>\n                                                                        </sheetData>\n                                                                        <pageMargins    left="0.7"    right="0.7"    top="0.75"    bottom="0.75"    header="0.3"    footer="0.3"/>\n                                                                </worksheet>\n                                                                ')
    got = _xml_to_list(fh.getvalue())
    self.assertEqual(got, exp)
