[Python-Dev] PEP: Frequently-requested additional features for the `unittest` module

Thu Jul 17 06:48:50 CEST 2008

Ben Finney wrote:
> Scott David Daniels <Scott.Daniels at Acm.Org> writes:> 
>> I would rather something more like:
>>>> def assert_compare_true(op, first, second, msg=None):
>> if op(first, second):
>> return
>> raise self.failure_exception(msg)
>> if msg is None:
>> self.failure_exception("%(first)r %(op)r %(second)"
>> % vars())
>> self.failure_exception("%(first)r %(op)r %(second): %(msg)"
>> % vars())
> I'm confused. It appears to me that your version never gets past the
> first 'raise' statement, which is unconditional; and the rest seems to
> do nothing but instantiate exceptions without using them.

Sorry, I was too hasty last time (had to jet out of the house) and sent
out the unfinished version. This is what I meant:
 def assert_compare_true(op, first, second, msg=None):
 if op(first, second):
 return
 if msg is None:
 raise self.failure_exception(
 "%(first)r %(op)r %(second)" % vars())
 raise self.failure_exception(
 "%(first)r %(op)r %(second): %(msg)" % vars())
(1) Displaying args is the whole point, otherwise just use assert_.
 This form fosters tests that say what is wrong, and not simply
 _that_ something has gone wrong.
 The point is a readable test, reducing boilerplate at the
 call location. Something like:
 ...
 self.assert_le(sum(source) // len(source), 5, "Mean OK")
(2) No point to doing string conversion except on failure; slow
 __repr__ methods are fine to use if the result is not discarded.
--Scott David Daniels
Scott.Daniels at Acm.Org