From f73be7c6900f2c69bf8a1eb85fa8440f6105c7d7 Mon Sep 17 00:00:00 2001
From: vmoens <vincentmoens@gmail.com>
Date: Wed, 22 Oct 2025 14:30:37 -0700
Subject: [PATCH] Update

[ghstack-poisoned]
---
 test/test_weightsync.py  | 24 ++++++++++++------------
 torchrl/envs/libs/gym.py |  7 ++++++-
 2 files changed, 18 insertions(+), 13 deletions(-)

diff --git a/test/test_weightsync.py b/test/test_weightsync.py
index 5da43accf7c..f5a4515f224 100644
--- a/test/test_weightsync.py
+++ b/test/test_weightsync.py
@@ -9,11 +9,11 @@
 import pytest
 import torch
 import torch.nn as nn
+from mocking_classes import ContinuousActionVecMockEnv
 from tensordict import TensorDict
 from tensordict.nn import TensorDictModule
 from torch import multiprocessing as mp
 from torchrl.collectors import MultiSyncDataCollector, SyncDataCollector
-from torchrl.envs import GymEnv
 from torchrl.weight_update.weight_sync_schemes import (
     _resolve_model,
     MPTransport,
@@ -274,7 +274,7 @@ def test_no_weight_sync_scheme(self):
 class TestCollectorIntegration:
     @pytest.fixture
     def simple_env(self):
-        return GymEnv("CartPole-v1")
+        return ContinuousActionVecMockEnv()
 
     @pytest.fixture
     def simple_policy(self, simple_env):
@@ -291,7 +291,7 @@ def test_syncdatacollector_multiprocess_scheme(self, simple_policy):
         scheme = MultiProcessWeightSyncScheme(strategy="state_dict")
 
         collector = SyncDataCollector(
-            create_env_fn=lambda: GymEnv("CartPole-v1"),
+            create_env_fn=ContinuousActionVecMockEnv,
             policy=simple_policy,
             frames_per_batch=64,
             total_frames=128,
@@ -316,8 +316,8 @@ def test_multisyncdatacollector_multiprocess_scheme(self, simple_policy):
 
         collector = MultiSyncDataCollector(
             create_env_fn=[
-                lambda: GymEnv("CartPole-v1"),
-                lambda: GymEnv("CartPole-v1"),
+                ContinuousActionVecMockEnv,
+                ContinuousActionVecMockEnv,
             ],
             policy=simple_policy,
             frames_per_batch=64,
@@ -343,8 +343,8 @@ def test_multisyncdatacollector_shared_mem_scheme(self, simple_policy):
 
         collector = MultiSyncDataCollector(
             create_env_fn=[
-                lambda: GymEnv("CartPole-v1"),
-                lambda: GymEnv("CartPole-v1"),
+                ContinuousActionVecMockEnv,
+                ContinuousActionVecMockEnv,
             ],
             policy=simple_policy,
             frames_per_batch=64,
@@ -369,7 +369,7 @@ def test_collector_no_weight_sync(self, simple_policy):
         scheme = NoWeightSyncScheme()
 
         collector = SyncDataCollector(
-            create_env_fn=lambda: GymEnv("CartPole-v1"),
+            create_env_fn=ContinuousActionVecMockEnv,
             policy=simple_policy,
             frames_per_batch=64,
             total_frames=128,
@@ -385,7 +385,7 @@ def test_collector_no_weight_sync(self, simple_policy):
 
 class TestMultiModelUpdates:
     def test_multi_model_state_dict_updates(self):
-        env = GymEnv("CartPole-v1")
+        env = ContinuousActionVecMockEnv()
 
         policy = TensorDictModule(
             nn.Linear(
@@ -407,7 +407,7 @@ def test_multi_model_state_dict_updates(self):
         }
 
         collector = SyncDataCollector(
-            create_env_fn=lambda: GymEnv("CartPole-v1"),
+            create_env_fn=ContinuousActionVecMockEnv,
             policy=policy,
             frames_per_batch=64,
             total_frames=128,
@@ -438,7 +438,7 @@ def test_multi_model_state_dict_updates(self):
         env.close()
 
     def test_multi_model_tensordict_updates(self):
-        env = GymEnv("CartPole-v1")
+        env = ContinuousActionVecMockEnv()
 
         policy = TensorDictModule(
             nn.Linear(
@@ -460,7 +460,7 @@ def test_multi_model_tensordict_updates(self):
         }
 
         collector = SyncDataCollector(
-            create_env_fn=lambda: GymEnv("CartPole-v1"),
+            create_env_fn=ContinuousActionVecMockEnv,
             policy=policy,
             frames_per_batch=64,
             total_frames=128,
diff --git a/torchrl/envs/libs/gym.py b/torchrl/envs/libs/gym.py
index a5c43d2ad23..ee34ab87185 100644
--- a/torchrl/envs/libs/gym.py
+++ b/torchrl/envs/libs/gym.py
@@ -1255,7 +1255,12 @@ def _build_gym_env(self, env, pixels_only):  # noqa: F811
 
     @property
     def lib(self) -> ModuleType:
-        return gym_backend()
+        gym = gym_backend()
+        if gym is None:
+            raise RuntimeError(
+                "Gym backend is not available. Please install gym or gymnasium."
+            )
+        return gym
 
     def _set_seed(self, seed: int | None) -> None:  # noqa: F811
         if self._seed_calls_reset is None: