Verifying a specific parameter with Moq

Question

public void SubmitMessagesToQueue_OneMessage_SubmitSuccessfully()
{
    var messageServiceClientMock = new Mock<IMessageServiceClient>();
    var queueableMessage = CreateSingleQueueableMessage();
    var message = queueableMessage[0];
    var xml = QueueableMessageAsXml(queueableMessage);
    messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(xml)).Verifiable();
    //messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(It.IsAny<XmlElement>())).Verifiable();

    var serviceProxyFactoryStub = new Mock<IMessageServiceClientFactory>();
    serviceProxyFactoryStub.Setup(proxyFactory => proxyFactory.CreateProxy()).Returns(essageServiceClientMock.Object);
    var loggerStub = new Mock<ILogger>();

    var client = new MessageClient(serviceProxyFactoryStub.Object, loggerStub.Object);
    client.SubmitMessagesToQueue(new List<IMessageRequestDTO> {message});

    //messageServiceClientMock.Verify(proxy => proxy.SubmitMessage(xml), Times.Once());
    messageServiceClientMock.Verify();
}

I'm starting using Moq and struggling a bit. I'm trying to verify that messageServiceClient is receiving the right parameter, which is an XmlElement, but I can't find any way to make it work. It works only when I don't check a particular value.

Any ideas?

Partial answer: I've found a way to test that the xml sent to the proxy is correct, but I still don't think it's the right way to do it.

public void SubmitMessagesToQueue_OneMessage_SubmitSuccessfully()
{
    var messageServiceClientMock = new Mock<IMessageServiceClient>();
    messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(It.IsAny<XmlElement>())).Verifiable();
    var serviceProxyFactoryStub = new Mock<IMessageServiceClientFactory>();
    serviceProxyFactoryStub.Setup(proxyFactory => proxyFactory.CreateProxy()).Returns(messageServiceClientMock.Object);
    var loggerStub = new Mock<ILogger>();

    var client = new MessageClient(serviceProxyFactoryStub.Object, loggerStub.Object);
    var message = CreateMessage();
    client.SubmitMessagesToQueue(new List<IMessageRequestDTO> {message});

    messageServiceClientMock.Verify(proxy => proxy.SubmitMessage(It.Is<XmlElement>(xmlElement => XMLDeserializer<QueueableMessage>.Deserialize(xmlElement).Messages.Contains(message))), Times.Once());
}

By the way, how could I extract the expression from the Verify call?

Answer 1

If the verification logic is non-trivial, it will be messy to write a large lambda method (as your example shows). You could put all the test statements in a separate method, but I don't like to do this because it disrupts the flow of reading the test code.

Another option is to use a callback on the Setup call to store the value that was passed into the mocked method, and then write standard Assert methods to validate it. For example:

// Arrange
MyObject saveObject;
mock.Setup(c => c.Method(It.IsAny<int>(), It.IsAny<MyObject>()))
        .Callback<int, MyObject>((i, obj) => saveObject = obj)
        .Returns("xyzzy");

// Act
// ...

// Assert
// Verify Method was called once only
mock.Verify(c => c.Method(It.IsAny<int>(), It.IsAny<MyObject>()), Times.Once());
// Assert about saveObject
Assert.That(saveObject.TheProperty, Is.EqualTo(2));