De-duplicate some unit test paramatrization

xarray/tests/test_units/params.py

@@ -0,0 +1,34 @@
+import pytest
+
+pint = pytest.importorskip("pint")
+from xarray.tests.test_units.pint import unit_registry
+
+
+def parametrize_unit_compatibility(error, allow_compatible_unit=True):
+    return pytest.mark.parametrize(
+        "unit,error",
+        (
+            pytest.param(1, error, id="no_unit"),
+            pytest.param(unit_registry.dimensionless, error, id="dimensionless"),
+            pytest.param(unit_registry.s, error, id="incompatible_unit"),
+            pytest.param(
+                unit_registry.mm,
+                None if allow_compatible_unit else error,
+                id="compatible_unit",
+            ),
+            pytest.param(unit_registry.m, None, id="identical_unit"),
+        ),
+        ids=repr,
+    )
+
+
+parametrize_variant = pytest.mark.parametrize(
+    "variant",
+    (
+        "data",
+        pytest.param(
+            "dims", marks=pytest.mark.skip(reason="indexes don't support units")
+        ),
+        "coords",
+    ),
+)

xarray/tests/test_units/pint.py

@@ -0,0 +1,7 @@
+import pytest
+
+pint = pytest.importorskip("pint")
+
+# make sure scalars are converted to 0d arrays so quantities can
+# always be treated like ndarrays
+unit_registry = pint.UnitRegistry(force_ndarray_like=True)