def test_childString(self):
        """
        Calling C{str()} with a C{URLPath.child()} will return a URL which is
        the child of the URL it was instantiated with.
        """
        self.assertEqual(str(self.path.child(b'hello')),
                         "http://example.com/foo/bar/hello")
        self.assertEqual(str(self.path.child(b'hello').child(b'')),
                         "http://example.com/foo/bar/hello/")
        self.assertEqual(str(self.path.child(b'hello', keepQuery=True)),
                         "http://example.com/foo/bar/hello?yes=no&no=yes")

        Calling C{str()} with a C{URLPath.child()} will return a URL which is
        the child of the URL it was instantiated with.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_urlpath.py