Use unittest-style tests

[jvkersch]

fixes #439

The first few commits are concerned with turning nose-style tests into unittest test cases (this was done in a semi-automatic way, with lots of Emacs macros). The remaining commits do the following:

• Make each tests folder into a package
• Rename test module to start with test_ so that it can be picked up by the unittest discovery runner
• Make each test have at least one assert (some tests would check something and then print a pass/fail message to stdout, others would just print things and not even do any checking).

Along the way, I did some minor cleanup (removing unused print statements, rewriting overly complicated six constructs, etc). I also made it so that the backend tests are run as part of the test suite: now that PyQt is easily installed, there is no need to keep these tests separate.

[corranwebster]

Generally looks good. A couple of minor questions, and the major issue that it isn't actually running any tests in CI right now.

[jvkersch]

@corranwebster Tests pass (and are actually running this time). I think I've addressed your comments, would you like to give this another look?

[jvkersch]

Actually, I marked one test as an expectedFailure that requires a bit more looking into (it fails because of a warning raised in Traits).

[jvkersch]

@corranwebster I've fixed up the issue with the expected failure, and I think this is good to go. Would you mind giving this a last look?

[corranwebster]

Being a bit picky here, but I think this is changing the global state of the warning filters but not resetting it, and so could affect the outcome of other tests which mess with warnings. Unfortunately this looks awkward to do in the warnings module withot messing with warnings.filter directly.

[jvkersch]

I don't think this is an issue here, since it's wrapped in a catch_warnings block which will reset the filters upon exit:

In [1]: import warnings

In [2]: print(warnings.filters)
[('default', re.compile('', re.IGNORECASE), <class 'DeprecationWarning'>, re.compile('__main__'), 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'BytesWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)]

In [3]: with warnings.catch_warnings(record=True) as w:
   ...:     warnings.filterwarnings("ignore", 'elementwise == comparison failed')
   ...:     print(warnings.filters)
   ...:     
[('ignore', re.compile('elementwise == comparison failed', re.IGNORECASE), <class 'Warning'>, re.compile(''), 0), ('default', re.compile('', re.IGNORECASE), <class 'DeprecationWarning'>, re.compile('__main__'), 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'BytesWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)]

In [4]: print(warnings.filters)
[('default', re.compile('', re.IGNORECASE), <class 'DeprecationWarning'>, re.compile('__main__'), 0), ('ignore', None, <class 'DeprecationWarning'>, None, 0), ('ignore', None, <class 'PendingDeprecationWarning'>, None, 0), ('ignore', None, <class 'ImportWarning'>, None, 0), ('ignore', None, <class 'BytesWarning'>, None, 0), ('ignore', None, <class 'ResourceWarning'>, None, 0)]

[corranwebster]

Cool, I didn't realise that.

[corranwebster]

LGTM

[jvkersch]

Thanks @corranwebster !