@requires_pinio mass disables unrelated tests

[crusaderky]

I think I'm losing my sanity here.
I have a anaconda3 Python 3.6 environment with all required and optional dependencies of xarray installed and updated to the latest available version, except pyNio.
If I run test.py on the latest xarray package from the git tip, the vast majority of the tests in test_backends.py are skipped - including those that have nothing to do with pyNio!
e.g.

tests/test_backends.py::ScipyInMemoryDataTest::test_bytesio_pickle PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_coordinates_encoding SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_dataset_caching SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_dataset_compute SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_default_fill_value SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_encoding_kwarg SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_encoding_same_dtype SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_invalid_dataarray_names_raise SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_load SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_orthogonal_indexing PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_pickle SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_pickle_dataarray SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_None_variable SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_boolean_dtype SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_coordinates SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_datetime_data SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_endian SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_example_1_netcdf SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_float64_data SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_mask_and_scale SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_object_dtype SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_string_data SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_strings_with_fill_value SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_test_data SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_timedelta_data SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_to_netcdf_explicit_engine PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_unsigned_roundtrip_mask_and_scale SKIPPED
tests/test_backends.py::ScipyInMemoryDataTest::test_write_store PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_zero_dimensional_variable SKIPPED

If I comment out line 1462:

@requires_scipy 
# @requires_pynio 
class TestPyNio(CFEncodedDataTest, Only32BitTypes, TestCase): 

Then magically everything starts working again!

tests/test_backends.py::ScipyInMemoryDataTest::test_bytesio_pickle PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_coordinates_encoding PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_dataset_caching PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_dataset_compute PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_default_fill_value PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_encoding_kwarg PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_encoding_same_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_invalid_dataarray_names_raise PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_load PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_orthogonal_indexing PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_pickle PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_pickle_dataarray PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_None_variable PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_boolean_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_coordinates PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_datetime_data PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_endian PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_example_1_netcdf PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_float64_data PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_mask_and_scale PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_object_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_string_data PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_strings_with_fill_value PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_test_data PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_roundtrip_timedelta_data PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_to_netcdf_explicit_engine PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_unsigned_roundtrip_mask_and_scale PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_write_store PASSED
tests/test_backends.py::ScipyInMemoryDataTest::test_zero_dimensional_variable PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_bytesio_pickle PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_coordinates_encoding PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_dataset_caching PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_dataset_compute PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_default_fill_value PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_encoding_kwarg PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_encoding_same_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_invalid_dataarray_names_raise PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_load PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_orthogonal_indexing PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_pickle PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_pickle_dataarray PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_None_variable PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_boolean_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_coordinates PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_datetime_data PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_endian PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_example_1_netcdf PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_float64_data PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_mask_and_scale PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_object_dtype PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_string_data PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_strings_with_fill_value PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_test_data PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_roundtrip_timedelta_data PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_to_netcdf_explicit_engine PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_unsigned_roundtrip_mask_and_scale PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_write_store PASSED
tests/test_backends.py::ScipyInMemoryDataTestAutocloseTrue::test_zero_dimensional_variable PASSED

[shoyer]

Yes, this is surprising. I don't know why this is happening, but apparently it's not just happening to you (see @rabernat's complaint in #1528).

[rabernat]

I discovered you can force the tests to run by doing e.g.

pytest -v xarray/tests/test_backends.py::ScipyInMemoryDataTest

Then they are not skipped. I don't know if this is a useful clue or not.

[jhamman]

likely bug reported in pytest-dev/pytest#2759