ENH: Informative dtype message for for assert_series_equal (pandas-dev#28993)

Author: moi90

pandas/tests/util/test_assert_frame_equal.py

@@ -141,7 +141,7 @@ def test_empty_dtypes(check_dtype):
     df1["col1"] = df1["col1"].astype("int64")
 
     if check_dtype:
-        msg = "Attributes are different"
+        msg = r"Attributes of DataFrame\..* are different"
         with pytest.raises(AssertionError, match=msg):
             assert_frame_equal(df1, df2, **kwargs)
     else:

pandas/tests/util/test_assert_series_equal.py

@@ -179,7 +179,7 @@ def test_series_equal_values_mismatch(check_less_precise):
 
 
 def test_series_equal_categorical_mismatch(check_categorical):
-    msg = """Attributes are different
+    msg = """Attributes of Series are different
 
 Attribute "dtype" are different
 \\[left\\]:  CategoricalDtype\\(categories=\\['a', 'b'\\], ordered=False\\)

pandas/util/testing.py

@@ -1156,7 +1156,9 @@ def assert_series_equal(
         ):
             pass
         else:
-            assert_attr_equal("dtype", left, right)
+            assert_attr_equal(
+                "dtype", left, right, obj="Attributes of {obj}".format(obj=obj)
+            )
 
     if check_exact:
         assert_numpy_array_equal(
@@ -1315,8 +1317,9 @@ def assert_frame_equal(
 
     >>> assert_frame_equal(df1, df2)
     Traceback (most recent call last):
-    AssertionError: Attributes are different
     ...
+    AssertionError: Attributes of DataFrame.iloc[:, 1] are different
+
     Attribute "dtype" are different
     [left]:  int64
     [right]: float64