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

def test_siblingString(self):

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