private void testReadWrite(Random rng, Writer wr) throws InterruptedException {
ArrayBlockingQueue<byte[]> q = newQueue();
InputStream is = create(q);
wr.init(q);
wr.start();
Reader rd = new Reader(rng, is);
rd.run();
wr.join();
Assert.assertNull(wr.exn);
Assert.assertNull(rd.exn);
System.out.printf("sums %x -> %x\n", wr.getSum(), rd.getSum());
Assert.assertEquals(wr.getSum(), rd.getSum());
}