[TIP] adding custom tests to a unittest test run

[Chris Jerdonek]

On Wed, May 16, 2012 at 6:27 AM, Marius Gedminas <marius at gedmin.as> wrote:
> On Tue, May 15, 2012 at 09:25:28PM -0700, Chris Jerdonek wrote:
>> I often have the need to add extra tests to my unittest.main() test
>> runs.  The tests I need to add are tests that depend on data obtained
>> at run-time, e.g. user-provided command-line options.
>
> I'm used to the following idiom for this:
>
>    def test_suite():
>        tests = unittest.TestSuite(...)
>        if some_condition:
>            tests.addTests(...)
>        if some_condition:
>            tests.addTests(...)
>        return tests
>
>    if __name__ == '__main__':
>        unittest.main(defaultTest='test_suite')
>
> Although in real life I'll use a test runner (such as zope.testrunner)
> that will add up all the tests returned by test_suite() in all of my
> test modules, instead of relying on unittest.main().

I'm interested in solutions that don't require setting (and then
reading) some kind of global state prior to loading tests.

In the solution above, the test loader will invoke test_suite()
without arguments, so there is no way to pass data to the function
without relying on global state (e.g. setting a variable on a module).

I see now that the load_tests protocol might be another possibility.
unittest.main()'s calls to load_tests pass the arguments (loader,
tests, pattern), where loader is a TestLoader instance, so perhaps the
needed data could be attached to a loader, and the loader passed as
the testLoader argument to unittest.main().  That solution doesn't
seem very elegant, but it looks like it would do the job.

>> So far, the best I've come up with is the below.  Is there a better
>> solution?  What do others recommend?
>>
>> [Also see: https://gist.github.com/2707352 ]
>
> I find this code difficult to understand.

That's why I'm e-mailing this list. :) I'd like to know if there is a
simpler, more straightforward solution I'm missing.

--Chris