def test_immutability(self):
s = State(x=1)
ss = Dup(1).run(s).result()
s.x = 2
self.assertEqual(ss[0].x, 1)
def test_basic(self):
s = State(x=1)
self.assertEqual(Dup(0).run(s).result(), States())
self.assertEqual(Dup(1).run(s).result(), States(s))
self.assertEqual(Dup(2).run(s).result(), States(s, s))