def loadTestsFromModule(self, module, pattern=None):
        """Return a suite of all tests cases contained in the given module

        If the module is a package, load tests from all the modules in it.
        If the module has an ``additional_tests`` function, call it and add
        the return value to the tests.
        """
        if module in self._visited:
            return None
        self._visited.add(module)

        tests = []
        tests.append(TestLoader.loadTestsFromModule(self, module))

        if hasattr(module, "additional_tests"):
            tests.append(module.additional_tests())

        if hasattr(module, '__path__'):
            for file in resource_listdir(module.__name__, ''):
                if file.endswith('.py') and file != '__init__.py':
                    submodule = module.__name__ + '.' + file[:-3]
                else:
                    if resource_exists(module.__name__, file + '/__init__.py'):
                        submodule = module.__name__ + '.' + file
                    else:
                        continue
                tests.append(self.loadTestsFromName(submodule))

        if len(tests) != 1:
            return self.suiteClass(tests)
        else:
            return tests[0]  # don't create a nested suite for only one return
Return a suite of all tests cases contained in the given module

        If the module is a package, load tests from all the modules in it.
        If the module has an ``additional_tests`` function, call it and add
        the return value to the tests.
        
product/gradle-plugin/src/main/python/setuptools/command/test.py