Data vars in open mfdataset (#1623)

* make tests more explicit

Author: guziy

xarray/tests/test_backends.py

@@ -1340,19 +1340,10 @@ def test_common_coord_when_datavars_all(self):
 
                 var_shape = ds[self.var_name].shape
 
-                # shape pairs to be compared
-                shape_pairs = [
-                    (var_shape, coord_shape),
-                    (coord_shape1, coord_shape),
-                    (coord_shape2, coord_shape)
-                ]
-                # tests to be applied to respective pairs
-                tests = [self.assertEqual,
-                         self.assertNotEqual, self.assertNotEqual]
-
-                for a_test, a_shape_pair in zip(tests, shape_pairs):
-                    a_test(*a_shape_pair)
-
+                self.assertEqual(var_shape, coord_shape)
+                self.assertNotEqual(coord_shape1, coord_shape)
+                self.assertNotEqual(coord_shape2, coord_shape)
+      
     def test_common_coord_when_datavars_minimal(self):
         opt = 'minimal'
 
@@ -1366,18 +1357,9 @@ def test_common_coord_when_datavars_minimal(self):
 
                 var_shape = ds[self.var_name].shape
 
-                # shape pairs to be compared
-                shape_pairs = [
-                    (var_shape, coord_shape),
-                    (coord_shape1, coord_shape),
-                    (coord_shape2, coord_shape)
-                ]
-                # tests to be applied to respective pairs
-                tests = [self.assertNotEqual,
-                         self.assertEqual, self.assertEqual]
-
-                for a_test, a_shape_pair in zip(tests, shape_pairs):
-                    a_test(*a_shape_pair)
+                self.assertNotEqual(var_shape, coord_shape)
+                self.assertEqual(coord_shape1, coord_shape)
+                self.assertEqual(coord_shape2, coord_shape)
 
     def test_invalid_data_vars_value_should_fail(self):