mark tests as needed kerchunk dependency

virtualizarr/tests/test_backend.py

@@ -309,13 +309,15 @@ def test_virtualizarr_vs_local_nisar(self, hdf_backend):
         xrt.assert_equal(dsXR, dsV)
 
 
+@requires_kerchunk
 def test_open_empty_group(empty_netcdf4_file):
     vds = open_virtual_dataset(empty_netcdf4_file, indexes={})
     assert isinstance(vds, xr.Dataset)
     expected = Dataset()
     xrt.assert_identical(vds, expected)
 
 
+@requires_kerchunk
 class TestOpenVirtualDatasetHDFGroup:
     def test_open_subgroup(self, netcdf4_file_with_data_in_multiple_groups):
         vds = open_virtual_dataset(
@@ -343,10 +345,6 @@ def test_open_root_group_by_default(
         assert isinstance(vds["foo"].data, ManifestArray)
         assert vds["foo"].shape == (3,)
 
-    def test_raise_on_nonexistent_group(self): ...
-
-    def test_open_empty_group(self): ...
-
 
 @requires_kerchunk
 class TestLoadVirtualDataset: