+
+
+class TestEmpty:
+
+ def test_repr(self):
+ self.assertEqual(repr(Empty), 'Empty')
+
+ def test_isempty(self):
+ self.assertTrue(Empty.isempty())
+
+ def test_isuniverse(self):
+ self.assertFalse(Empty.isuniverse())
+
+
+class TestUniverse:
+
+ def test_repr(self):
+ self.assertEqual(repr(Universe), 'Universe')
+
+ def test_isempty(self):
+ self.assertTrue(Universe.isempty())
+
+ def test_isuniverse(self):
+ self.assertTrue(Universe.isuniverse())