issues: 1006335177

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id node_id number title user state locked assignee milestone comments created_at updated_at closed_at author_association active_lock_reason draft pull_request body reactions performed_via_github_app state_reason repo type
1006335177 I_kwDOAMm_X847-3TJ 5814 Confusing assertion message when comparing datasets with differing coordinates 4160723 open 0     1 2021-09-24T10:50:11Z 2021-09-24T15:17:00Z   MEMBER      

What happened: When two datasets a and b have only differing coordinates, xr.testing.assert_* may output a confusing message that also reports differing data variables (although strictly equal/identical) sharing common dimensions with those differing coordinates. I guess it is because when comparing the data variables we compare DataArray objects (thus including the coordinates).

What you expected to happen: An output assertion error message that shows only the differing coordinates.

Minimal Complete Verifiable Example:

```python

import xarray as xr a = xr.Dataset(data_vars={"var": ("x", [10.0, 11.0])}, coords={"x": [0, 1]}) b = xr.Dataset(data_vars={"var": ("x", [10.0, 11.0])}, coords={"x": [2, 3]}) xr.testing.assert_equal(a, b) AssertionError: Left and right Dataset objects are not equal

Differing coordinates: L * x (x) int64 0 1 R * x (x) int64 2 3 Differing data variables: L var (x) float64 10.0 11.0 R var (x) float64 10.0 11.0 ```

I would rather expect:

```python

xr.testing.assert_equal(a, b) AssertionError: Left and right Dataset objects are not equal

Differing coordinates: L * x (x) int64 0 1 R * x (x) int64 2 3 ```

Anything else we need to know?:

Environment:

Output of <tt>xr.show_versions()</tt> INSTALLED VERSIONS ------------------ commit: None python: 3.9.6 | packaged by conda-forge | (default, Jul 11 2021, 03:36:15) [Clang 11.1.0 ] python-bits: 64 OS: Darwin OS-release: 20.3.0 machine: x86_64 processor: i386 byteorder: little LC_ALL: None LANG: None LOCALE: (None, 'UTF-8') libhdf5: 1.10.6 libnetcdf: 4.7.4 xarray: 0.19.1.dev72+ga8d84c703.d20210901 pandas: 1.3.2 numpy: 1.21.2 scipy: 1.7.1 netCDF4: 1.5.6 pydap: installed h5netcdf: 0.8.1 h5py: 3.3.0 Nio: None zarr: 2.6.1 cftime: 1.5.0 nc_time_axis: 1.2.0 PseudoNetCDF: installed rasterio: 1.2.1 cfgrib: 0.9.8.5 iris: 3.0.4 bottleneck: 1.3.2 dask: 2021.01.1 distributed: 2021.01.1 matplotlib: 3.4.3 cartopy: 0.18.0 seaborn: 0.11.1 numbagg: None fsspec: 0.8.5 cupy: None pint: 0.16.1 sparse: 0.11.2 setuptools: 57.4.0 pip: 20.2.4 conda: None pytest: 6.2.5 IPython: 7.27.0 sphinx: 3.3.1 
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