If the author can keep the whole function code_change -> relevant E2E_TESTS in his head, it seems to be a trivial application. We don't know the methodology, s

If the author can keep the whole function code_change -> relevant E2E_TESTS in his head, it seems to be a trivial application. We don't know the methodology, since the author does not state how he verified that function or how he would verify the function for a large code base.