human
I wrote the below code

    called = []
    def assert_correct_xml_output(filename, doc):
        called.append(True)
        expect(doc.toxml).when.called.doesnt.throw(UnicodeDecodeError)
    old = xunit_output.write_xml_doc
    xunit_output.write_xml_doc = assert_correct_xml_output
    runner = Runner(feature_name('xunit_unicode_and_bytestring_mixing'), enable_xunit=True)
    try:
        runner.run()
    finally:
        xunit_output.write_xml_doc = old

What's a good function header?
assistant
#Here's a good function header.

@with_setup(prepare_stdout, registry.clear)
def test_xunit_xml_output_with_no_errors():