g t g t - 2 months ago 48
C# Question

Using Moq to verify calls are made in the correct order

I need to test the following method:

CreateOutput(IWriter writer)
{
writer.Write(type);
writer.Write(id);
writer.Write(sender);

// many more Write()s...
}


I've created a Moq'd
IWriter
and I want to ensure that the
Write()
methods are called in the right order.

I have the following test code:

var mockWriter = new Mock<IWriter>(MockBehavior.Strict);
var sequence = new MockSequence();
mockWriter.InSequence(sequence).Setup(x => x.Write(expectedType));
mockWriter.InSequence(sequence).Setup(x => x.Write(expectedId));
mockWriter.InSequence(sequence).Setup(x => x.Write(expectedSender));


However, the second call to
Write()
in
CreateOutput()
(to write the
id
value) throws a
MockException
with the message "IWriter.Write() invocation failed with mock behavior Strict. All invocations on the mock must have a corresponding setup.".

I'm also finding it hard to find any definitive, up-to-date documentation/examples of Moq sequences.

Am I doing something wrong, or can I not set up a sequence using the same method?
If not, is there an alternative I can use (preferably using Moq/NUnit)?

Answer

There is bug when using MockSequence on same mock. It definitely will be fixed in later releases of Moq library (you can also fix it manually by changing Moq.MethodCall.Matches implementation).

If you want to use Moq only, then you can verify method call order via callbacks:

int callOrder = 0;
writerMock.Setup(x => x.Write(expectedType)).Callback(() => Assert.That(callOrder++, Is.EqualTo(0)));
writerMock.Setup(x => x.Write(expectedId)).Callback(() => Assert.That(callOrder++, Is.EqualTo(1)));
writerMock.Setup(x => x.Write(expectedSender)).Callback(() => Assert.That(callOrder++, Is.EqualTo(2)));