def test_stdinOut(self):
        sys = FakeSys(["eliotfilter", "J[0]"], b"[1, 2]\n[4, 5]\n")
        main(sys)
        self.assertEqual(sys.stdout.getvalue(), b"1\n4\n")
L{main} reads from the C{stdin} attribute of the given C{sys} equivalent,
dataset/ETHPy150Open ClusterHQ/eliot/eliot/tests/test_filter.py/MainTests.test_stdinOut