issue_comments

That seems sensible to me. It would also be a good way to ensure that XArray operations adhere to all of the dask.array checks.

from dask.array.utils import assert_eq

In the dask library itself we solve this by creating our own assert_eq functions that both invoke the single-threaded scheduler, and also do a variety of other sanity checks like ensuring that the expected and computed dtypes and shapes are the same, that the keynames in graphs are sensible, etc..

I can remove all the mock related code from test_dask.py entirely and test_dataarray_with_dask_coords still passes.

It was just a guess. Something wacky is certainly happening though. I recommend copying my code from my last comment and running pytest on it either in the root directory or in xarray/tests. I found that the outcome differed depending on location.

I still don't understand what actually went wrong here. It looks like we have test coverage for calling compute on an xarray.DataArray (see test_dataarray_with_dask_coords), but even though the exact example from that test fails at the repl the test passes when called with pytest:

I experienced some odd behavior when testing this within the XArray test suite

This file would pass when within xarray/tests/ but would fail when within the root directory

```python import numpy as np import xarray as xr import dask

def test_dask_reduction(): data = xr.DataArray(np.random.random(size=(10, 2)), dims=['samples', 'features']).chunk((5, 2)) result = dask.compute(data.mean(axis=0)) ```

I suspect some odd behavior around mock, but that's probably due to a general bias/lack of understanding of that module.

See https://github.com/pydata/xarray/pull/1760 for a potential fix

Also worth pointing out that this is likely the kind of bug that would have been caught with static typing

On Mon, Dec 4, 2017 at 6:55 PM, Stephan Hoyer notifications@github.com wrote:

Any objection to having the .compute methods point to dask.compute if the dask.version is appropriate?

Yes, this seems like a small win.

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Any objection to having the .compute methods point to dask.compute if the dask.__version__ is appropriate?

Here is the problem. It was just a silly typo.

```diff diff --git a/xarray/core/dataarray.py b/xarray/core/dataarray.py index 0516b47..263860d 100644 --- a/xarray/core/dataarray.py +++ b/xarray/core/dataarray.py @@ -594,7 +594,7 @@ class DataArray(AbstractArray, BaseDataObject):

 @property
 def __dask_scheduler__(self):

• return self._to_temp_dataset().dask_optimize

• return self._to_temp_dataset().dask_scheduler

  def dask_postcompute(self): func, args = self._to_temp_dataset().dask_postcompute() ```

@shoyer any suggestions on comprehensive ways to test things?

While testing this I oddly learn that the following line makes this pass

python from xarray.tests import mock

I'll take a look