add a static method to compare indexing overators

Author: keewis

xarray_array_testing/base.py

@@ -2,7 +2,9 @@
 from abc import ABC
 from types import ModuleType
 
+import numpy as np
 import numpy.testing as npt
+import xarray as xr
 from xarray.namedarray._typing import duckarray
 
 
@@ -24,3 +26,23 @@ def array_strategy_fn(*, shape, dtype):
     @staticmethod
     def assert_equal(a, b):
         npt.assert_equal(a, b)
+
+    @staticmethod
+    def assert_dimension_indexers_equal(a, b):
+        assert type(a) is type(b), f"types don't match: {type(a)} vs {type(b)}"
+
+        if isinstance(a, dict):
+            assert a.keys() == b.keys(), f"Different dimensions: {list(a)} vs {list(b)}"
+
+            values = ((a[k], b[k]) for k in a)
+            assert all(
+                (
+                    isinstance(v1, xr.Variable)
+                    and isinstance(v2, xr.Variable)
+                    and v1.dims == v2.dims
+                    and np.equal(v1.data, v2.data)
+                )
+                for v1, v2 in values
+            ), "Differing indexers"
+        else:
+            npt.assert_equal(a, b)