Verify() with custom failure message

[mpdelbuono]

When using Verifiable() setups, a call to Verify() is used without any parameters to verify that the expected calls were made. However, sometimes I would like to put a custom failure message to include some extra data (for example, a RNG seed that generated the data for the test).

The other overloads of Verify() support a failMessage parameter, but there does not appear to be any Verify(string failMessage) which would be used for tests that use Verifiable().

It would be nice if we could add this in. (When I find some free time I might just implement this and make a PR for this, but I wanted to at least get some thoughts on it first, because perhaps there's a reason this is missing.)

[stakx]

If I understand you correctly, you would like to inject additional information not specific to any one particular setup into the verification error message, and the proposed Verify(string failMessage) would be the means to do just that. Correct?

I don't think that this functionality has to be provided by Moq. The unit testing framework of your choice likely already gives you the means to log additional information per test:

• xUnit.net can inject (via your test fixture's constructor) a ITestOutputHelper, which you can use to log messages. (See their documentation page "Capturing output".)

• NUnit has TestContext.Out.

• MSTest has TestContext.WriteLine.

In my opinion it would be preferable to just use these mechanisms instead of reinventing the wheel in Moq. While mock.Verify(string failMessage) would seem a logical addition that "completes" the current API, keep in mind that the likely use case for setup.Verifiable(string failMessage) is to make it easier for you to identify that particular setup in cases where your test has a great number of similar setups. A mock.Verify(string failMessage) won't provide the same benefit.

Example for xUnit.net and Visual Studio:

using Moq;
using Xunit;
using Xunit.Abstractions;

public interface IFrobbler
{
    void Frobble();
}

public class Tests
{
    private ITestOutputHelper log;

    public Tests(ITestOutputHelper log)
    {
        this.log = log;
    }

    [Fact]
    public void FailingTest()
    {
        this.log.WriteLine("(Random number generator seed goes here.)");

        var mock = new Mock<IFrobbler>();
        mock.Setup(m => m.Frobble());
        mock.VerifyAll();
    }
}

[mpdelbuono]

I did not realize there was a setup.Verifiable(string failMessage) :)

Your argument that setup-specific probably makes more sense. While in my case I would have the same information for each Verifiable() call, I think my case is unusual. setup.Verifiable(string failMessage) works for me.

[stakx]

To be clear, I wasn't saying that you should use setup.Verifiable(failMessage) for general logging of any useful error information. I was saying that this particular method is useful to make setups more easily identifiable, and that you should use your testing framework's facilities for general logging.

I'm glad you found a solution that works for you. I'll close this then.