[Python-Dev] unittest's redundant assertions: asserts vs. failIf/Unlesses

[Steven D'Aprano]

On Mon, 14 Jul 2008 12:45:58 am Michael Foord wrote:

> I tend to think of testing as action followed by assertion -
> I do this and this should have happened. Your tests usually define
> 'expected behaviour' rather than defining how your code won't fail...

Who is the "your" that you are speaking for there? It isn't me.

I tend to think of tests as *both* expected behaviour and unexpected 
behaviour: sometimes a test is most naturally written as "this should 
happen" and sometimes as "this shouldn't happen". It depends on what 
I'm testing.

When it comes to test-driven development, I will often start by 
thinking "What test can I write to make this code fail?" -- not "what 
test can I write to make this code pass?". Having come up with a 
failure mode, the test is often most naturally written as "fail if" 
or "fail unless", and I resent having to turn the condition around into 
a "assert if not" test just to satisfy others who are never going to 
read my code. I wish people would go find another bike shed to 
interfere with.


-- 
Steven