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On Fri, Nov 21, 2014 at 05:23:28PM -0500, Matthew Treinish wrote:
> On Fri, Nov 21, 2014 at 04:15:07PM -0500, Sean Dague wrote:
> > On 11/21/2014 01:52 PM, Matthew Treinish wrote:
> > > On Fri, Nov 21, 2014 at 07:15:49PM +0100, jordan pittier wrote:
> > >> Hey,
> > >> I am not a Nova developer but I still have an opinion.
> > >>
> > >>> Using boolean assertions
> > >> I like what you propose. We should use and enforce the assert* that best matches the intention. It's about semantic and the more precise we are, the better.
> > >>
> > >>> Using same order of arguments in equality assertions
> > >> Why not. But I don't know how we can write a Hacking rule for this. So you may fix all the occurrences for this now, but it might get back in the future.
> > > 
> > > Ok I'll bite, besides the enforceability issue which you pointed out, it just
> > > doesn't make any sense, you're asserting 2 things are equal: (A == B) == (B == A)
> > > and I honestly feel that it goes beyond nitpicking because of that. 
> > > 
> > > It's also a fallacy that there will always be an observed value and an
> > > expected value. For example:
> > > 
> > >   self.assertEqual(method_a(), method_b())
> > > 
> > > Which one is observed and which one is expected? I think this proposal is just
> > > reading into the parameter names a bit too much.
> > 
> > If you are using assertEqual with 2 variable values... you are doing
> > your test wrong.
> > 
> > I was originally in your camp. But honestly, the error message provided
> > to the user does say expected and observed, and teaching everyone that
> > you have to ignore the error message is a much harder thing to do than
> > flip the code to conform to it, creating less confusion.
> > 
> 
> Uhm, no it doesn't, the default error message is "A != B". [1][2][3] (both with
> unittest and testtools) If the error message was like that, then sure saying
> one way was right over the other would be fine, (assuming you didn't specify a
> different error message) but, that's not what it does.
> 
> 
> [1] https://github.com/testing-cabal/testtools/blob/master/testtools/testcase.py#L340
> [2] https://github.com/testing-cabal/testtools/blob/master/testtools/matchers/_basic.py#L85 
> [3] https://hg.python.org/cpython/file/301d62ef5c0b/Lib/unittest/case.py#l508

...
  File "/opt/stack/nova/.venv/lib/python2.7/site-packages/testtools/testcase.py", line 348, in assertEqual
    self.assertThat(observed, matcher, message)
  File "/opt/stack/nova/.venv/lib/python2.7/site-packages/testtools/testcase.py", line 433, in assertThat
    raise mismatch_error
MismatchError: !=:
reference = {'nova_object.changes': ['cells'],
 'nova_object.data': {...
actual    = {'nova_object.changes': ['cells'],
 'nova_object.data': {...
...