Tests for module-level functions with units (#3493)

* add tests for replication functions

* add tests for `xarray.dot`

* add tests for apply_ufunc

* explicitly set the test ids to repr

* add tests for align

* cover a bit more of align

* add tests for broadcast

* black changed how tuple unpacking should look like

* correct the xfail message for full_like tests

* add tests for where

* add tests for concat

* add tests for combine_by_coords

* fix a bug in convert_units

* convert the align results to the same units

* rename the combine_by_coords test

* convert the units for expected in combine_by_coords

* add tests for combine_nested

* add tests for merge with datasets

* only use three datasets for merging

* add tests for merge with dataarrays

* update whats-new.rst

doc/whats-new.rst

@@ -118,7 +118,8 @@ Internal Changes
 ~~~~~~~~~~~~~~~~
 
 - Added integration tests against `pint <https://pint.readthedocs.io/>`_.
-  (:pull:`3238`, :pull:`3447`, :pull:`3508`) by `Justus Magin <https://github.com/keewis>`_.
+  (:pull:`3238`, :pull:`3447`, :pull:`3493`, :pull:`3508`)
+  by `Justus Magin <https://github.com/keewis>`_.
 
   .. note::