Gymnasium/tests/utils/test_env_checker.py

from typing import Optional

import gym
import numpy as np
import pytest
from gym.spaces import Box, Dict, Discrete

from gym.utils.env_checker import check_env


class ActionDictTestEnv(gym.Env):
    action_space = Dict({"position": Discrete(1), "velocity": Discrete(1)})
    observation_space = Box(low=-1.0, high=2.0, shape=(3,), dtype=np.float32)

    def step(self, action):
        observation = np.array([1.0, 1.5, 0.5])
        reward = 1
        done = True
        return observation, reward, done

    def reset(self, seed: Optional[int] = None):
        super().reset(seed=seed)
        return np.array([1.0, 1.5, 0.5])

    def render(self, mode="human"):
        pass


def test_check_env_dict_action():
    # Environment.step() only returns 3 values: obs, reward, done. Not info!
    test_env = ActionDictTestEnv()

    with pytest.raises(AssertionError) as errorinfo:
        check_env(env=test_env, warn=True)
        assert (
            str(errorinfo.value)
            == "The `step()` method must return four values: obs, reward, done, info"
        )