def test_size(self):
s = Sustitucion()
self.assertEqual(s.size(), 0)
s.push(1, 2)
self.assertEqual(s.size(), 1)
s.pop()
self.assertEqual(s.size(), 0)
def test_push(self):
s = Sustitucion()
self.assertEqual(s.size(), 0)
s.push(Var("a"), Int())
self.assertEqual(s.size(), 1)
