fix tests

Author: dcherian

xarray/core/groupby.py

@@ -587,7 +587,7 @@ def _flox_reduce(self, dim, **kwargs):
             ):
                 raise ValueError(f"cannot reduce over dimensions {dim}.")
 
-        # TODO: handle bins=N in dask_groupby
+        # TODO: handle bins=N in flox
         if self._bins is not None:
             expected_groups = (self._bins,)
             isbin = (True,)
@@ -600,6 +600,9 @@ def _flox_reduce(self, dim, **kwargs):
                     # note min_count makes no sense in the xarray world
                     # as a kwarg for count, so this should be OK
                     kwargs["min_count"] = 1
+            # empty bins have np.nan regardless of dtype
+            # flox's default would not set np.nan for integer dtypes
+            kwargs.setdefault("fill_value", np.nan)
         else:
             expected_groups = (self._unique_coord.values,)
             isbin = False

xarray/tests/test_units.py

@@ -5320,8 +5320,12 @@ def test_computation_objects(self, func, variant, dtype):
         units = extract_units(ds)
 
         args = [] if func.name != "groupby" else ["y"]
-        expected = attach_units(func(strip_units(ds)).mean(*args), units)
-        actual = func(ds).mean(*args)
+        # Doesn't work with flox because pint doesn't implement
+        # ufunc.reduceat or np.bincount
+        #  kwargs = {"engine": "numpy"} if "groupby" in func.name else {}
+        kwargs = {}
+        expected = attach_units(func(strip_units(ds)).mean(*args, **kwargs), units)
+        actual = func(ds).mean(*args, **kwargs)
 
         assert_units_equal(expected, actual)
         assert_allclose(expected, actual)