Issue pandas-dev#26101

Author: Sandeep P

pandas/util/testing.py

@@ -1001,6 +1001,12 @@ def assert_series_equal(left, right, check_dtype=True,
     obj : str, default 'Series'
         Specify object name being compared, internally used to show appropriate
         assertion message.
+
+        When comparing two numbers, if the first number has magnitude less
+        than 1e-5, we compare the two numbers directly and check whether
+        they are equivalent within the specified precision. Otherwise, we
+        compare the **ratio** of the second number to the first number and
+        check whether it is equivalent to 1 within the specified precision.
     """
     __tracebackhide__ = True
 
@@ -1153,7 +1159,13 @@ def assert_frame_equal(left, right, check_dtype=True,
     obj : str, default 'DataFrame'
         Specify object name being compared, internally used to show appropriate
         assertion message.
-
+        
+        When comparing two numbers, if the first number has magnitude less
+        than 1e-5, we compare the two numbers directly and check whether
+        they are equivalent within the specified precision. Otherwise, we
+        compare the **ratio** of the second number to the first number and
+        check whether it is equivalent to 1 within the specified precision.
+        
     See Also
     --------
     assert_series_equal : Equivalent method for asserting Series equality.