def findTestClasses(self, module):
        """Given a module, return all Trial test classes"""
        classes = []
        for name, val in inspect.getmembers(module):
            if isTestCase(val):
                classes.append(val)
        return self.sort(classes)
Given a module, return all Trial test classes
stackoverflow/venv/lib/python3.6/site-packages/twisted/trial/runner.py