Mocking IEndpointInstance with NSubstitute

[ivanm...@gmail.com]

Hi,

In NSB v5 I could mock the IBus and then use methods like received from the mocking lib to test whether the IBus.Send(..) received the expected arguments or not. When I try to mock IEndpointInstance in the same way, I get a System.ArgumentNullException:

Is this behavior by design or not?

And yes, I can use TestableEndpointInstance to achieve the same, and that works. 

I'm using NSubstitute for mocking, and reading the last comment form this SO (https://stackoverflow.com/questions/46226952/how-to-mock-out-iendpointinstance-of-nservicebus#_=_), it says that this can be achieved using Moq, so I wonder why this does not work with NSubstitute.

My NSB v5 test with IBus that works fine:

var ibus = Substitute.For<IBus>();

_myService.DoSomething(objectWithSomeParams); //this one calls IBus.Send(MyMessage)

            

ibus.Received().Send(Arg.Any<MyMessage>());

My NSB v6 test with IEndpointInstance that throws exception:

var endpointInstance = Substitute.For<IEndpointInstance>();

_myService.DoSomething(objectWithSomeParams); //this one calls IEndpointInstance.Send(MyMessage)
           
endpointInstance.Received().Send(Arg.Any<MyMessage>());

//throws following exception:
(System.ArgumentNullException : Value cannot be null.
Parameter name: message
   at NServiceBus.IMessageSessionExtensions.Send(IMessageSession session, Object message) in C:\BuildAgent\work\3206e2123f54fce4\src\NServiceBus.Core\IMessageSessionExtensions.cs:line 19)

Current refactor that does the same without mocking

var testableEndpointInstance = new TestableEndpointInstance();

_myService.DoSomething(objectWithSomeParams); //this one calls IEndpointInstance.Send(MyMessage)

var sentMessages = testableEndpointInstance.SentMessages;
sentMessages.Length.ShouldBe(1);
sentMessages[0].Message.ShouldBeOfType<MyMessage>();

[Daniel Marbach]

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