add h5netcdf for complex model tests, raise on invalid engine

tests/models/cross/test_hilbert_cpcca.py

@@ -67,7 +67,7 @@ def test_singular_values(use_pca):
 
 
 # Currently, netCDF4 does not support complex numbers, so skip this test
-@pytest.mark.parametrize("engine", ["zarr"])
+@pytest.mark.parametrize("engine", ["h5netcdf", "zarr"])
 @pytest.mark.parametrize("alpha", [0.0, 0.5, 1.0])
 def test_save_load_with_data(tmp_path, engine, alpha):
     """Test save/load methods in CPCCA class, ensuring that we can

tests/models/single/test_pop.py

@@ -155,7 +155,7 @@ def test_inverse_transform(mock_data_array):
     assert set(X_rec.dims) == set(mock_data_array.dims)
 
 
-@pytest.mark.parametrize("engine", ["zarr"])
+@pytest.mark.parametrize("engine", ["h5netcdf", "zarr"])
 def test_save_load(mock_data_array, tmp_path, engine):
     """Test save/load methods in POP class, ensuring that we can
     roundtrip the model and get the same results when transforming

tests/utilities.py

@@ -155,7 +155,9 @@ def skip_if_missing_engine(engine: str):
     """
     Skip save/load tests if missing the i/o backend.
     """
-    # xarray uses engine="netcdf4" but the package itself is called "netCDF4".
-    mapping = {"netcdf4": "netCDF4"}
-    module = mapping.get(engine, engine)
+    # xarray uses engine="netcdf4" but the package itself is "netCDF4".
+    mapping = {"h5netcdf": "h5netcdf", "netcdf4": "netCDF4", "zarr": "zarr"}
+    module = mapping.get(engine)
+    if module is None:
+        raise ValueError(f"Unrecognized engine: {engine}")
     pytest.importorskip(module)