added netCDF4 requirement to failing tests

xarray/tests/test_backends.py

@@ -2777,6 +2777,7 @@ def test_dump_encodings_h5py(self):
 
 
 @requires_h5netcdf
+@requires_netCDF4
 class TestH5NetCDFAlreadyOpen:
     def test_open_dataset_group(self):
         import h5netcdf
@@ -5162,11 +5163,12 @@ def test_open_fsspec():
 
 
 @requires_h5netcdf
+@requires_netCDF4
 def test_load_single_value_h5netcdf(tmp_path):
     """Test that numeric single-element vector attributes are handled fine.
 
     At present (h5netcdf v0.8.1), the h5netcdf exposes single-valued numeric variable
-    attributes as arrays of length 1, as oppesed to scalars for the NetCDF4
+    attributes as arrays of length 1, as opposed to scalars for the NetCDF4
     backend.  This was leading to a ValueError upon loading a single value from
     a file, see #4471.  Test that loading causes no failure.
     """