Fix test_dataarray.TestDataArray.test_expand_dims_with_greater_dim_size tests to pass in python 3.5 using ordered dicts instead of regular dicts. This was needed because python 3.5 and earlier did not maintain insertion order for dicts

Author: pletchm

xarray/tests/test_dataarray.py

@@ -1403,25 +1403,43 @@ def test_expand_dims_with_scalar_coordinate(self):
         assert_identical(array, roundtripped)
 
     def test_expand_dims_with_greater_dim_size(self):
+        """Python 3.6+ dicts keep insertion order, unlike Python 3.5 and
+        earlier. Therefore the following tests have to use ordered dicts to
+        pass for python 3.5 and earlier.
+        """
         array = DataArray(np.random.randn(3, 4), dims=['x', 'dim_0'],
                           coords={'x': np.linspace(0.0, 1.0, 3), 'z': 1.0},
                           attrs={'key': 'entry'})
-        actual = array.expand_dims({'y': 2, 'z': 1, 'dim_1': ['a', 'b', 'c']})
-
+        # For python 3.5 and earlier this has to be an ordered dict, to
+        # maintain insertion order.
+        actual = array.expand_dims(
+            OrderedDict((('y', 2), ('z', 1), ('dim_1', ['a', 'b', 'c']))))
+
+        expected_coords = OrderedDict((
+            ('y', [0, 1]), ('z', [1.0]), ('dim_1', ['a', 'b', 'c']),
+            ('x', np.linspace(0, 1, 3)), ('dim_0', range(4))))
         expected = DataArray(array.values * np.ones([2, 1, 3, 3, 4]),
-                             coords=dict(y=[0, 1],
-                                         z=[1.0],
-                                         dim_1=['a', 'b', 'c'],
-                                         x=np.linspace(0, 1, 3),
-                                         dim_0=range(4)),
-                             dims=['y', 'z', 'dim_1', 'x', 'dim_0'],
+                             coords=expected_coords,
+                             dims=list(expected_coords.keys()),
                              attrs={'key': 'entry'}
                              ).drop(['y', 'dim_0'])
         assert_identical(expected, actual)
 
         # Test with kwargs instead of passing dict to dim arg.
         other_way = array.expand_dims(y=2, z=1, dim_1=['a', 'b', 'c'])
-        assert_identical(expected, other_way)
+        # Unfortunately, there is no way to maintain insertion order with
+        # kwargs in python 3.5 and earlier, so for now we have to ensure the
+        # dimensions of the expected result are in the same order as the actual
+        # result to allow the test to pass.
+        other_way_expected_coords = OrderedDict()
+        for dim in other_way.dims:
+            other_way_expected_coords[dim] = expected_coords[dim]
+        other_way_expected = DataArray(
+            array.values * np.ones(list(other_way.shape)),
+            coords=other_way_expected_coords,
+            dims=list(other_way_expected_coords.keys()),
+            attrs={'key': 'entry'}).drop(['y', 'dim_0'])
+        assert_identical(other_way_expected, other_way)
 
     def test_set_index(self):
         indexes = [self.mindex.get_level_values(n) for n in self.mindex.names]