[Python-Dev] Proposed unittest changes

[Nick Coghlan]

Michael Foord wrote:
> Raymond Hettinger wrote:
>> From: "Ben Finney" <ben+python at benfinney.id.au>
>>> Right, so I'm putting up a separate PEP just for the renaming. Should
>>> be arriving on this list soon.
>>
>> I would like to work with you or someone else who is interested
>> on an alternative PEP for a separate, simpler test module
>> using the py.test syntax.  That is much simpler to learn and use.
>> Instead of self.assertIsNot and whatnot, you write:
>>   assert a is not b
>> No need for tons of word-by-word spellings on things we already
>> have syntax for.  Almost anyone who has used py.test can attest
>> its syntax is much more natural, easy to learn, easy to both
>> read and write, and is much lighter weight.  I think some variant
>> of py.test could be done that is compatable with unittest
>> and the did not have the "magic" present in earlier versions of py.test.
> 
> Ah, in my haste I skipped over your comment about "magic", my apologies. 
> But in the absence of magic how do you propose to provide a meaningful 
> error message from the failure of:
> 
> assert a == b
> 
> To wrap it in a function like "assert equals(a, b)" seems to gain little 
> over unittest.

Aside from the question of providing nice error messages, two questions 
that immediately come to mind for me are:
- how do I run my tests with -O or -OO? (since the compiler will throw 
all the assert statements away before any Python code gets a chance to 
look at them)
- how do I test that code raises an expected exception?
- how do I explicitly fail a test case? (e.g. I'll often do this when I 
want to test an operation with a variety of different inputs - I'll test 
for all of the inputs of interest, collecting the failures in a list, 
then reporting a single error message at the end detailing all of the 
cases that failed)

And I've also never had any problem whatsoever debugging unit tests with 
print statements - one of the effects of the -v switch is to display 
anything which is written to stderr/stdout on the console again.

Cheers,
Nick.

-- 
Nick Coghlan   |   ncoghlan at gmail.com   |   Brisbane, Australia
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