def test_largeReturn(self):
        """
        Like L{test_largeWrite}, but for the case where C{render} returns a
        long string rather than explicitly passing it to L{Request.write}.
        """
        class LargeReturn(resource.Resource):
            def render(self, request):
                return b'x' * SIZE_LIMIT + b'y'

        request = self._requestTest(LargeReturn())
        request.addCallback(self.assertEqual, b'x' * SIZE_LIMIT + b'y')
        return request

        Like L{test_largeWrite}, but for the case where C{render} returns a
        long string rather than explicitly passing it to L{Request.write}.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/web/test/test_distrib.py