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Re: Case study: debugging failed assertRaises bug

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Steven D'Aprano <steve+comp.lang.python@pearwood.info> wrote:

> (1) assertRaises REALLY needs a better error message. If not a custom 
> message, at least it should show the result it got instead of an 
> exception.
> 
If a different exception was thrown then you get an error instead of a 
failure and you are shown the Exception that was thrown, so I think you 
only have an issue if no exception was thrown at all.

If so, here's an alternative way to write your test which might be easier 
to debug:

    def testBadArgType(self):
        # Test failures with bad argument types.
        for d in (None, 23, object(), "spam"):
            with self.assertRaises(TypeError) as cm:
                self.func(d)
                print(d, "didn't throw the exception")

It is worth remembering that print output doesn't appear unless the test 
fails, so you can leave the tracing statement in the test. Also, 
assertRaises has a weird dual life as a context manager: I never knew that 
before today.


-- 
Duncan Booth http://kupuguy.blogspot.com

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Case study: debugging failed assertRaises bug Steven D'Aprano <steve+comp.lang.python@pearwood.info> - 2011-04-26 06:05 +0000
  Re: Case study: debugging failed assertRaises bug Duncan Booth <duncan.booth@invalid.invalid> - 2011-04-26 09:22 +0000
  Re: Case study: debugging failed assertRaises bug Raymond Hettinger <python@rcn.com> - 2011-04-26 14:10 -0700
  Re: Case study: debugging failed assertRaises bug Ben Finney <ben+python@benfinney.id.au> - 2011-04-27 10:14 +1000
    Re: Case study: debugging failed assertRaises bug R David Murray <rdmurray@bitdance.com> - 2011-04-27 14:54 +0000

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