protected void verifyOnDemandQueues(MessageChannel y3, MessageChannel z3, Map<String, Object> initialTransportState) {
		QueueChannel y3q = (QueueChannel) y3;
		assertEquals(1, y3q.getQueueSize());
		QueueChannel z3q = (QueueChannel) z3;
		assertEquals(1, z3q.getQueueSize());
		final Message<?> yMessage = y3q.receive(2000);
		final Message<?> zMessage = z3q.receive(2000);
		assertEquals("y", yMessage.getPayload());
		assertEquals("z", zMessage.getPayload());
	}
Verifies the content of the queues

@param y3 the channel where the y's are sent
@param z3 the channel where the z's are sent
@param initialTransportState the initial state of the transport (can be ignored except for Kafka)
spring-xd-dirt/src/test/java/org/springframework/xd/dirt/stream/AbstractSingleNodeStreamDeploymentIntegrationTests.java