use pytest.warns instead of pytest.raises

Author: d-v-b

tests/test_dtype/test_npy/test_bytes.py

@@ -150,7 +150,7 @@ def test_unstable_dtype_warning(
     Test that we get a warning when serializing a dtype without a zarr v3 spec to json
     when zarr_format is 3
     """
-    with pytest.raises(UnstableSpecificationWarning):
+    with pytest.warns(UnstableSpecificationWarning):
         zdtype.to_json(zarr_format=3)
 
 

tests/test_dtype/test_npy/test_string.py

@@ -131,7 +131,7 @@ def test_unstable_dtype_warning(zdtype: FixedLengthUTF32 | VariableLengthUTF8) -
     Test that we get a warning when serializing a dtype without a zarr v3 spec to json
     when zarr_format is 3
     """
-    with pytest.raises(UnstableSpecificationWarning):
+    with pytest.warns(UnstableSpecificationWarning):
         zdtype.to_json(zarr_format=3)