def METHOD_NAME(self):
    infile = self._create_infile('{"key":"💩"}')
    outfile = os_helper.TESTFN + '.out'
    self.addCleanup(os.remove, outfile)
    assert_python_ok('-m', 'json.tool', infile, outfile)
    with open(outfile, "rb") as f:
        lines = f.read().splitlines()
    # asserting an ascii encoded output file
    expected = [b'{', rb'    "key": "\ud83d\udca9"', b"}"]
    self.assertEqual(lines, expected)