def test_should_return_a_value_if_a_value_exists_for_key(self):
database = KeyValueDatabase()
database.set("abc", "123")
self.assertEqual("123", database.get("abc"))
def test_should_return_none_when_no_value_exists_for_key(self):
database = KeyValueDatabase()
self.assertIsNone(database.get("abc"))
