In article <mailman.4872.1327005963.27778.python-l...@python.org>, Jabba Laci <jabba.l...@gmail.com> wrote:
> Hi, > > In a unit test, I want to verify that a function returns a > cookielib.LWPCookieJar object. What is the correct way of doing that? jar = my_function_being_tested() self.assertIsInstance(jar, cookielib.LWPCookieJar) That works in 2.7. If you're using something older than 2.7, you'll need to do: self.assertTrue(isinstance(jar, cookielib.LWPCookieJar) Alternatively, just download the 2.7 version of unittest and use that (it works fine with 2.6, not sure about earlier than that). > 3) isinstance(return_value, cookielib.LWPCookieJar) seems to be the > best way, however somewhere I read that using isinstance is > discouraged Where did you read that, and in what context? Compared to type(), isinstance() is an improvement because it correctly handles subclasses. If you want a LWPCookieJar, you should be happy to have somebody give you a subclass of LWPCookieJar (assuming they correctly implemented the interface). Thus says the Church of Most Corpulent Staticness and Type Bondage. On the other hand, there are some (adherents of the Most Holy and Loquacious Church of Duck Typing) who would say that testing for class at all is a sin, and what you want to do is test that the object being tested has the methods and attributes you expect. Me, I'm somewhere in between. I believe that pinching it and seeing what the quack sounds like is usually the right thing to do. On the other hand, if you want to demand to see its Certificate of Duckiness, you have a right to do that too. -- http://mail.python.org/mailman/listinfo/python-list