Add test for MedicalImage feature without MONAI

tests/package/base.py

@@ -1,5 +1,6 @@
 """Test import of subpackages with base cyclops install."""
 
+import numpy as np
 import pytest
 
 
@@ -21,3 +22,27 @@ def test_import_cyclops():
         import cyclops.monitor
     with pytest.raises(ImportError):
         import cyclops.report
+
+
+def test_medical_image_feature_without_monai():
+    """Test that the MedicalImage feature raises an error without MONAI installed."""
+    from cyclops.data.features.medical_image import MedicalImage
+
+    feat = MedicalImage()
+    # create a dummy image
+    img = np.random.rand(10, 10, 10)
+
+    # test encode_example
+    with pytest.raises(
+        RuntimeError,
+        match="The MONAI library is required to use the `MedicalImage` feature.*",
+    ):
+        feat.encode_example(img)
+
+    # test decode_example
+    dummy_val = {"path": "/dummy/local/path", "bytes": None}
+    with pytest.raises(
+        RuntimeError,
+        match="The MONAI library is required to use the `MedicalImage` feature.*",
+    ):
+        feat.decode_example(dummy_val)