attachments.put("bar", new DataHandler(new StringDataSource("barValue")));
eventContext = createEventContext(null, attachments);
eventContext.getMessage().removeOutboundAttachment("baz");
InvocationResult response = invokeResolver("processAttachmentsOptional", eventContext);
assertTrue("Message payload should be a Map", response.getResult() instanceof Map);
Map<String, DataHandler> result = (Map<String, DataHandler>) response.getResult();
assertEquals(2, result.size());
assertEquals("fooValue", readAttachment(result.get("foo")));
assertEquals("barValue", readAttachment(result.get("bar")));
assertNull(result.get("baz"));
}