Add test for DataTree

Author: mjwillson

xarray/tests/test_datatree.py

@@ -2423,6 +2423,43 @@ def test_arithmetic_inherited_coords(self) -> None:
         expected["/foo/bar"].data = np.array([8, 10, 12])
         assert_identical(actual, expected)
 
+    def test_binary_op_compat_setting(self) -> None:
+        # Setting up a clash of non-index coordinate 'foo':
+        a = DataTree(xr.Dataset(
+            data_vars={"var": (["x"], [0, 0, 0])},
+            coords={
+                "x": [1, 2, 3],
+                "foo": (["x"], [1.0, 2.0, np.nan]),
+            },
+        ))
+        b = DataTree(xr.Dataset(
+            data_vars={"var": (["x"], [0, 0, 0])},
+            coords={
+                "x": [1, 2, 3],
+                "foo": (["x"], [np.nan, 2.0, 3.0]),
+            },
+        ))
+
+        with xr.set_options(arithmetic_compat="minimal"):
+            expected = DataTree(a.dataset.drop_vars('foo'))
+            assert_equal(a + b, expected)
+
+        with xr.set_options(arithmetic_compat="override"):
+            assert_equal(a + b, a)
+            assert_equal(b + a, b)
+
+        with xr.set_options(arithmetic_compat="no_conflicts"):
+            expected = DataTree(a.dataset.assign_coords(
+                foo=(["x"], [1.0, 2.0, 3.0])))
+            assert_equal(a + b, expected)
+            assert_equal(b + a, expected)
+
+        with xr.set_options(arithmetic_compat="equals"):
+            with pytest.raises(xr.MergeError):
+                a + b
+            with pytest.raises(xr.MergeError):
+                b + a
+
     def test_binary_op_commutativity_with_dataset(self) -> None:
         # regression test for #9365