'Gather unique suite objects from loaded things. This will guarantee
uniqueness of inherited methods on TestCases which would otherwise hash
to same value and collapse to one test unexpectedly if using simpler
means: e.g. set().'

def _uniqueTests(self, things):

    seen = set()
    for testthing in things:
        testthings = testthing._tests
        for thing in testthings:
            if (str(thing) not in seen):
                (yield thing)
                seen.add(str(thing))
