'Calling C{str()} with a C{URLPath.child()} will return a URL which is
the child of the URL it was instantiated with.'

def test_childString(self):

    self.assertEqual(str(self.path.child('hello')), 'http://example.com/foo/bar/hello')
    self.assertEqual(str(self.path.child('hello').child('')), 'http://example.com/foo/bar/hello/')
    self.assertEqual(str(self.path.child('hello', keepQuery=True)), 'http://example.com/foo/bar/hello?yes=no&no=yes')
