diff --git a/test/base/test_utils.py b/test/base/test_utils.py
index bd14ffe..1d8e37c 100644
--- a/test/base/test_utils.py
+++ b/test/base/test_utils.py
@@ -1,10 +1,12 @@
 import numpy as np
 import torch
+from torch import nn
 
 from tianshou.exploration import GaussianNoise, OUNoise
 from tianshou.utils import MovAvg, MultipleLRSchedulers, RunningMeanStd
 from tianshou.utils.net.common import MLP, Net
 from tianshou.utils.net.continuous import RecurrentActorProb, RecurrentCritic
+from tianshou.utils.torch_utils import in_eval_mode, in_train_mode
 
 
 def test_noise() -> None:
@@ -132,9 +134,17 @@ def test_lr_schedulers() -> None:
     )
 
 
-if __name__ == "__main__":
-    test_noise()
-    test_moving_average()
-    test_rms()
-    test_net()
-    test_lr_schedulers()
+def test_in_eval_mode():
+    module = nn.Linear(3, 4)
+    module.train()
+    with in_eval_mode(module):
+        assert not module.training
+    assert module.training
+
+
+def test_in_train_mode():
+    module = nn.Linear(3, 4)
+    module.eval()
+    with in_train_mode(module):
+        assert module.training
+    assert not module.training
\ No newline at end of file
diff --git a/tianshou/trainer/utils.py b/tianshou/trainer/utils.py
index 4d990db..b790fdd 100644
--- a/tianshou/trainer/utils.py
+++ b/tianshou/trainer/utils.py
@@ -27,7 +27,7 @@ def test_episode(
     collector.reset(reset_stats=False)
     if test_fn:
         test_fn(epoch, global_step)
-    result = collector.collect(n_episode=n_episode, is_eval=True)
+    result = collector.collect(n_episode=n_episode, eval_mode=True)
     if reward_metric:  # TODO: move into collector
         rew = reward_metric(result.returns)
         result.returns = rew
diff --git a/tianshou/utils/torch_utils.py b/tianshou/utils/torch_utils.py
new file mode 100644
index 0000000..1676b52
--- /dev/null
+++ b/tianshou/utils/torch_utils.py
@@ -0,0 +1,25 @@
+from contextlib import contextmanager
+
+from torch import nn
+
+
+@contextmanager
+def in_eval_mode(module: nn.Module) -> None:
+    """Temporarily switch to evaluation mode."""
+    train = module.training
+    try:
+        module.eval()
+        yield
+    finally:
+        module.train(train)
+
+
+@contextmanager
+def in_train_mode(module: nn.Module) -> None:
+    """Temporarily switch to training mode."""
+    train = module.training
+    try:
+        module.train()
+        yield
+    finally:
+        module.train(train)