def foo(x,y):
        """
        >>> foo(1,1)
        2
        >>> foo(1,1)
        3
        """
        return x+y

if __name__ == '__main__':
        import doctest
        doctest.testmod()



----------
[fawad@fawad5 ~]$ python foo.py
**********************************************************************
File "foo.py", line 5, in __main__.foo
Failed example:
    foo(1,1)
Expected:
    3
Got:
    2
**********************************************************************
1 items had failures:
   1 of   2 in __main__.foo
***Test Failed*** 1 failures.