Class MockIO

Lib/test/test_io.py:4170–4174

        chunk_size = 8192  # default chunk size, updated later

        class MockIO(self.MockRawIO):
            def write(self, data):
                if len(data) > chunk_size:
                    raise RuntimeError
                return super().write(data)

        buf = MockIO()
        t = self.TextIOWrapper(buf, encoding="ascii")