'The ``in`` operator reports that a :py:type:`set` not containing a
curve does not contain that curve.'

def test_does_not_contain(self):

    curve = get_elliptic_curve(self.curve_factory.curve_name)
    curves = set([get_elliptic_curve(self.curve_factory.another_curve_name)])
    self.assertNotIn(curve, curves)
