Cannot import xarray.tests due to use of pytest.config

[jjhelmus]

xarray.tests cannot be imported due to the use of pytest.config:

$ python -c "import xarray; print(xarray.__version__); import xarray.tests"
0.9.2-3-g9479038
Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/home/jhelmus/devel/xarray/xarray/tests/__init__.py", line 118, in <module>
    not pytest.config.getoption("--run-flaky"),
AttributeError: module 'pytest' has no attribute 'config'

The use of pytest.config in the xarray/tests/__init__.py seem to have been introduced in #1336. From the discussion in pytest-dev/pytest#1688 it seems as if the use of pytest.config is discouraged.

[jjhelmus]

pytest-dev/pytest#472 from BitBucket #472 seems to touch on this topic and references the note found at the end of the skip and xfail documentation:

You cannot use pytest.config.getvalue() in code imported before pytest’s argument parsing takes place.
For example, conftest.py files are imported before command line parsing and thus config.getvalue() will not execute correctly.

[shoyer]

Hmm. This seems like an easy way to add a few options to running our test suite, but maybe there is a better way to do this? I guess we could hack in a fallback with hasattr() but that's pretty ugly.

Just out of curiosity, what reason did you have for importing xarray.tests?

[jjhelmus]

Just out of curiosity, what reason did you have for importing xarray.tests?

xarray.tests is listed as a import test in the conda-forge xarray-feedstock and was failing when I was doing a build. I do not think that import line needs to be present, tests does not seem to be in the public API of xarray. I'd be in favor of removing that line and keeping the test suite setup as-is.

[shoyer]

@jjhelmus Agreed! For testing public API, being able to import xarray and xarray.backends should be enough.

[shoyer]

@jjhelmus see conda-forge/xarray-feedstock#20

[jjhelmus]

@shoyer Agreed, there is no need for xarray.tests to be importable. Closing this issue, thanks for the quick clarification.