Part of twisted.trial.runner.TestLoader View Source
Return a test suite with all the tests from a module.
Included are TestCase subclasses and doctests listed in the module's
__doctests__ module. If that's not good for you, put a function named
either testSuite or test_suite in your module
that returns a TestSuite, and I'll use the results of that instead.
If testSuite and test_suite are both present,
then I'll use testSuite.