def test_invalidHeader(self):
        """
        A zipfile entry with the wrong magic number should raise BadZipfile for
        readfile(), but that should not affect other files in the archive.
        """
        fn = self.makeZipFile(["test contents",
                               "more contents"])
        with zipfile.ZipFile(fn, "r") as zf:
            zeroOffset = zf.getinfo("0").header_offset
        # Zero out just the one header.
        with open(fn, "r+b") as scribble:
            scribble.seek(zeroOffset, 0)
            scribble.write(b'0' * 4)
        with zipstream.ChunkingZipFile(fn) as czf:
            self.assertRaises(zipfile.BadZipfile, czf.readfile, "0")
            with czf.readfile("1") as zfe:
                self.assertEqual(zfe.read(), b"more contents")

        A zipfile entry with the wrong magic number should raise BadZipfile for
        readfile(), but that should not affect other files in the archive.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/python/test/test_zipstream.py