Unit testing of Saga handlers in rebus and correlation issues - unit-testing

Question

I have this simple Saga in Rebus:
public void MySaga : Saga<MySagaData>
IAmInitiatedBy<Event1>
IHandleMessages<Event2>
{
private IBus bus;
private ILog logger;
public MySaga(IBus bus, ILog logger)
{
if (bus == null) throw new ArgumentNullException("bus");
if (logger == null) throw new ArgumentNullException("logger");
this.bus = bus;
this.logger = logger;
}
protected override void CorrelateMessages(ICorrelationConfig<MySagaData> config)
{
config.Correlate<Event>(m => m.MyObjectId.Id, s => s.Id);
config.Correlate<Event>(m => m.MyObjectId.Id, s => s.Id);
}
public Task Handle(Event1 message)
{
return Task.Run(() =>
{
this.Data.Id = message.MyObjectId.Id;
this.Data.State = MyEnumSagaData.Step1;
var cmd = new ResponseCommandToEvent1(message.MyObjectId);
bus.Send(cmd);
});
}
public Task Handle(Event2 message)
{
return Task.Run(() =>
{
this.Data.State = MyEnumSagaData.Step2;
var cmd = new ResponseCommandToEvent2(message.MyObjectId);
bus.Send(cmd);
});
}
}
and thanks to the kind mookid8000 I can test the saga using FakeBus and a SagaFixture:
[TestInitialize]
public void TestInitialize()
{
var log = new Mock<ILog>();
bus = new FakeBus();
fixture = SagaFixture.For<MySaga>(() => new MySaga(bus, log.Object));
idTest = new MyObjectId(Guid.Parse("1B2E7286-97E5-4978-B5B0-D288D71AD670"));
}
[TestMethod]
public void TestIAmInitiatedBy()
{
evt = new Event1(idTest);
fixture.Deliver(evt);
var testableFixture = fixture.Data.OfType<MySagaData>().First();
Assert.AreEqual(MyEnumSagaData.Step1, testableFixture.State);
// ... more asserts
}
[TestMethod]
public void TestIHandleMessages()
{
evt = new Event2(idTest);
fixture.Deliver(evt);
var testableFixture = fixture.Data.OfType<MySagaData>().First();
Assert.AreEqual(MyEnumSagaData.Step2, testableFixture.State);
// ... more asserts
}
[TestCleanup]
public void TestCleanup()
{
fixture.Dispose();
bus.Dispose();
}
The first test method that check IAmInitiatedBy is correctly executed and no error is thrown, while the second test fail. It looks like a correlation issues since fixture.Data contains no elements and in fixture.LogEvents contains as last elements this error: Could not find existing saga data for message Event2/b91d161b-eb1b-419d-9576-2c13cd9d9c51.
What is this GUID? Is completly different from the one I defined in the unit test? Any ideas? Is legal what I'm tryng to test (since I'm using an in-memory bus)?

Answer 1

This line is bad: this.Data.Id = message.MyObjectId.Id. If you checked the value of Data.Id before you overwrote it, you would have noticed that the property already had a value.
You do not assign the saga ID - Rebus does that. And you should leave that property alone :)
Regarding your error - when Rebus wants to log information about a specific message, it logs a short name for the type and the message ID, i.e. the value of the automatically-assigned rbs2-msg-id header. In other words: It's not the value of the property m.MyObjectId.Id, you're seeing, it's the message ID.
Since the saga fixture is re-initialized for every test run, and you only deliver an Event2 to it (which is not allowed to initiate a new instance), the saga will not be hit.