Mock Fabric os.environ variables to be sure to have a SingleDeviceStr…

…ategy Fabric object (#250)

sheeprl/utils/fabric.py

@@ -1,3 +1,5 @@
+from unittest import mock
+
 from lightning.fabric import Fabric
 from lightning.fabric.accelerators import XLAAccelerator
 from lightning.fabric.strategies import SingleDeviceStrategy, SingleDeviceXLAStrategy
@@ -23,4 +25,11 @@ def get_single_device_fabric(fabric: Fabric) -> Fabric:
         checkpoint_io=None,
         precision=fabric._precision,
     )
-    return Fabric(strategy=strategy)
+    with mock.patch.dict("os.environ") as mocked_os_environ:
+        mocked_os_environ.pop("LT_DEVICES", None)
+        mocked_os_environ.pop("LT_STRATEGY", None)
+        mocked_os_environ.pop("LT_NUM_NODES", None)
+        mocked_os_environ.pop("LT_PRECISION", None)
+        mocked_os_environ.pop("LT_ACCELERATOR", None)
+        fabric = Fabric(strategy=strategy)
+    return fabric

tests/test_utils/test_fabric.py

@@ -0,0 +1,13 @@
+from lightning import Fabric
+from lightning.fabric.strategies import SingleDeviceStrategy
+
+from sheeprl.utils.fabric import get_single_device_fabric
+
+
+def test_get_single_device_fabric():
+    fabric = Fabric(devices=2, accelerator="cpu", precision=16)
+    single_device_fabric = get_single_device_fabric(fabric)
+    assert single_device_fabric.device == fabric.device
+    assert single_device_fabric._precision == fabric._precision
+    assert single_device_fabric.accelerator == fabric.accelerator
+    assert isinstance(single_device_fabric.strategy, SingleDeviceStrategy)