@Test
 public void fourPeers() throws Exception {
   InboundMessageQueuer[] channels = {
     connectPeer(1), connectPeer(2), connectPeer(3), connectPeer(4)
   };
   Transaction tx = new Transaction(params);
   TransactionBroadcast broadcast = new TransactionBroadcast(peerGroup, tx);
   ListenableFuture<Transaction> future = broadcast.broadcast();
   assertFalse(future.isDone());
   // We expect two peers to receive a tx message, and at least one of the others must announce for
   // the future to
   // complete successfully.
   Message[] messages = {
     (Message) outbound(channels[0]),
     (Message) outbound(channels[1]),
     (Message) outbound(channels[2]),
     (Message) outbound(channels[3])
   };
   // 0 and 3 are randomly selected to receive the broadcast.
   assertEquals(tx, messages[0]);
   assertEquals(tx, messages[3]);
   assertNull(messages[1]);
   assertNull(messages[2]);
   Threading.waitForUserCode();
   assertFalse(future.isDone());
   inbound(channels[1], InventoryMessage.with(tx));
   pingAndWait(channels[1]);
   Threading.waitForUserCode();
   assertTrue(future.isDone());
 }