Initialize observation spaces and pytest (#2929)

* Remove step initialization for mujoco obs spaces

	* remove step initialization for mujoco obs space

	* pre-commit

pytest obs space mujoco

tests/envs/test_mujoco.py

@@ -3,6 +3,7 @@ import pytest
 
 import gym
 from gym import envs
+from gym.envs.registration import EnvSpec
 from tests.envs.utils import mujoco_testing_env_specs
 
 EPS = 1e-6
@@ -37,6 +38,65 @@ def verify_environments_match(
             break
 
 
+EXCLUDE_POS_FROM_OBS = [
+    "Ant",
+    "HalfCheetah",
+    "Hopper",
+    "Humanoid",
+    "Swimmer",
+    "Walker2d",
+]
+
+
+@pytest.mark.parametrize(
+    "env_spec",
+    mujoco_testing_env_specs,
+    ids=[env_spec.id for env_spec in mujoco_testing_env_specs],
+)
+def test_obs_space_mujoco_environments(env_spec: EnvSpec):
+    """Check that the returned observations are contained in the observation space of the environment"""
+    env = env_spec.make(disable_env_checker=True)
+    reset_obs = env.reset()
+    assert env.observation_space.contains(
+        reset_obs
+    ), f"Obseravtion returned by reset() of {env_spec.id} is not contained in the default observation space {env.observation_space}."
+
+    action = env.action_space.sample()
+    step_obs, _, _, _ = env.step(action)
+    assert env.observation_space.contains(
+        step_obs
+    ), f"Obseravtion returned by step(action) of {env_spec.id} is not contained in the default observation space {env.observation_space}."
+
+    if env_spec.name in EXCLUDE_POS_FROM_OBS and (
+        env_spec.version == 4 or env_spec.version == 3
+    ):
+        env = env_spec.make(
+            disable_env_checker=True, exclude_current_positions_from_observation=False
+        )
+        reset_obs = env.reset()
+        assert env.observation_space.contains(
+            reset_obs
+        ), f"Obseravtion of {env_spec.id} is not contained in the default observation space {env.observation_space} when excluding current position from observation."
+
+        step_obs, _, _, _ = env.step(action)
+        assert env.observation_space.contains(
+            step_obs
+        ), f"Obseravtion returned by step(action) of {env_spec.id} is not contained in the default observation space {env.observation_space} when excluding current position from observation."
+
+    # Ant-v4 has the option of including contact forces in the observation space with the use_contact_forces argument
+    if env_spec.name == "Ant" and env_spec.version == 4:
+        env = env_spec.make(disable_env_checker=True, use_contact_forces=True)
+        reset_obs = env.reset()
+        assert env.observation_space.contains(
+            reset_obs
+        ), f"Obseravtion of {env_spec.id} is not contained in the default observation space {env.observation_space} when using contact forces."
+
+        step_obs, _, _, _ = env.step(action)
+        assert env.observation_space.contains(
+            step_obs
+        ), f"Obseravtion returned by step(action) of {env_spec.id} is not contained in the default observation space {env.observation_space} when using contact forces."
+
+
 MUJOCO_V2_V3_ENVS = [
     spec.name
     for spec in mujoco_testing_env_specs