Recently while writing some tests to check that methods were called/not called in a Python 2.7 application, I noticed that assert_called() and assert_not_called() were always passing when they shouldn’t have been. Some googling lead me here, where I read that those methods don’t exist as of 12/1/15. That begged the question: if in fact these assertions don’t exist, why would they pass?

After some more fiddling, I managed to produce the error I expected: Setting autospec=True caused: AttributeError: 'function' object has no attribute 'assert_called_once'.

Okay, so it looks like the assertions really don’t exist.

To confirm: pip list mock showed I had Mock version 1.0.1 — and a quick perusal of the source verified that sure enough, they really didn’t exist!

That was a valuable lesson in mocking learned. Without autospeccing, I may have gone one to write a number of additional false-positive tests!