def test_same_length_responses(self):
        """Test len_reward when all responses have the same length."""
        completions = [
            [{"content": r"\boxed{\frac{63}{400}}"}],
            [{"content": r"\boxed{\frac{64}{400}}"}],
        ]
        solutions = [r"\frac{63}{400}", r"\frac{63}{400}"]

        rewards = len_reward(completions, solutions)
        self.assertEqual(rewards, [0.0, 0.0])
Test len_reward when all responses have the same length.
tests/test_rewards.py