Should we run tests on docstrings?

[max-sixty]

Currently almost none of the docstrings pass running pytest --doctest-modules xarray/core, though mostly for easy reasons.

Should we run these in CI?

I've recently started using docstring tests in another project, and they've work pretty well.

CC @keewis

[keewis]

👍 for running doctest in CI, this should help us keep the examples in sync with the implementation

[dcherian]

I second this. It seems to run quite quickly...