@Test
	public void testDontOverwriteHeaders() {
		String streamName = "testDontOverwrite";

		String headers = "{\"bar\":\"payload.substring(1)\"}";

		String processingChainUnderTest = String.format("%s --headers=%s --overwrite=false", moduleName, headers);

		chain = chain(application, streamName, processingChainUnderTest);
		Map<String, Object> messageHeaders = Collections.singletonMap("bar", (Object) "oldValue");
		Message<String> message = MessageBuilder.createMessage("hello", new MessageHeaders(messageHeaders));

		chain.send(message);
		Message<?> transformed = chain.receive(RECEIVE_TIMEOUT);
		assertEquals("oldValue", transformed.getHeaders().get("bar"));

	}
Start the single node container, binding random unused ports, etc. to not conflict with any other instances
running on this host. Configure the ModuleRegistry to include the project module.
extensions/spring-xd-extension-header-enricher/src/test/java/org/springframework/xd/header/enricher/HeaderEnricherIntegrationTests.java