'Test writing a chartsheet with no cell data.'

def test_assemble_xml_file(self):

    self.maxDiff = None
    fh = StringIO()
    chartsheet = Chartsheet()
    chartsheet._set_filehandle(fh)
    chartsheet.drawing = 1
    chartsheet._assemble_xml_file()
    exp = _xml_to_list('\n                                                                <?xml    version="1.0"    encoding="UTF-8"    standalone="yes"?>\n                                                                <chartsheet    xmlns="http://schemas.openxmlformats.org/spreadsheetml/2006/main"    xmlns:r="http://schemas.openxmlformats.org/officeDocument/2006/relationships">\n                                                                        <sheetPr/>\n                                                                        <sheetViews>\n                                                                                <sheetView    workbookViewId="0"/>\n                                                                        </sheetViews>\n                                                                        <pageMargins    left="0.7"    right="0.7"    top="0.75"    bottom="0.75"    header="0.3"    footer="0.3"/>\n                                                                        <drawing    r:id="rId1"/>\n                                                                </chartsheet>\n                                                                ')
    got = _xml_to_list(fh.getvalue())
    self.assertEqual(got, exp)
