Fix Pydap tests for numpy 2.3.0 changes (scalar string to unicode)

doc/whats-new.rst

@@ -24,6 +24,8 @@ Deprecations
 
 Bug fixes
 ~~~~~~~~~
+- Fix Pydap test_cmp_local_file for numpy 2.3.0 changes, 1. do always return arrays for all versions and 2. skip astype(str) for numpy >= 2.3.0 for expected data. (:pull:`10421`)
+  By `Kai Mühlbauer <https://github.com/kmuehlbauer>`_.
 
 
 Documentation

xarray/tests/test_backends.py

@@ -2274,7 +2274,7 @@
     # Flaky test. Very open to contributions on fixing this
     @pytest.mark.flaky
     def test_roundtrip_coordinates(self) -> None:
         super().test_roundtrip_coordinates()
 
     @requires_cftime
     def test_roundtrip_cftime_bnds(self):
@@ -5305,7 +5305,7 @@
     def test_dask_roundtrip(self) -> None:
         with create_tmp_file() as tmp:
             data = create_test_data()
             data.to_netcdf(tmp)
             chunks = {"dim1": 4, "dim2": 4, "dim3": 4, "time": 10}
             with open_dataset(tmp, chunks=chunks) as dask_ds:
                 assert_identical(data, dask_ds)
@@ -5417,11 +5417,12 @@
     @contextlib.contextmanager
     def create_datasets(self, **kwargs):
         with open_example_dataset("bears.nc") as expected:
+            # print("QQ0:", expected["bears"].load())
             pydap_ds = self.convert_to_pydap_dataset(expected)
             actual = open_dataset(PydapDataStore(pydap_ds))
-            # TODO solve this workaround:
-            # netcdf converts string to byte not unicode
-            expected["bears"] = expected["bears"].astype(str)
+            if Version(np.__version__) < Version("2.3.0"):
+                # netcdf converts string to byte not unicode
+                expected["bears"] = expected["bears"].astype(str)
             yield actual, expected
 
     def test_cmp_local_file(self) -> None:
@@ -5441,7 +5442,9 @@
             assert_equal(actual[{"l": 2}], expected[{"l": 2}])
 
         with self.create_datasets() as (actual, expected):
-            assert_equal(actual.isel(i=0, j=-1), expected.isel(i=0, j=-1))
+            # always return arrays and not scalars
+            # scalars will be promoted to unicode for numpy >= 2.3.0
+            assert_equal(actual.isel(i=[0], j=[-1]), expected.isel(i=[0], j=[-1]))
 
         with self.create_datasets() as (actual, expected):
             assert_equal(actual.isel(j=slice(1, 2)), expected.isel(j=slice(1, 2)))
@@ -5463,7 +5466,9 @@
             with create_tmp_file() as tmp_file:
                 actual.to_netcdf(tmp_file)
                 with open_dataset(tmp_file) as actual2:
-                    actual2["bears"] = actual2["bears"].astype(str)
+                    if Version(np.__version__) < Version("2.3.0"):
+                        # netcdf converts string to byte not unicode
+                        actual2["bears"] = actual2["bears"].astype(str)
                     assert_equal(actual2, expected)
 
     @requires_dask