Error message when attempting to mock an extension method

[gregsdennis]

I ran into an issue when I was (unwittingly) attempting to mock an extension method. I've seen #189, and I understand why I can't do that. Still, I think the error messaging could be better.

I have an interface:

public interface ILogger
{
    void Error(string);
}

and an extension method:

public void Error(this ILogger logger, Exception e)
{
    ...
}

and a test

[TestMethod]
public void TestIt()
{
	var logger = new Mock<ILogger>();
	logger.Verify(l => l.Error(It.IsAny<Exception>()));
}

As expected, the test fails. But why the test fails is confusing. The following error is returned:

Invalid verify on a non-virtual (overridable in VB) member: l => l.Error(It.IsAny())

The error says nothing about how Error(Exception) isn't even a member of ILogger.

[aKabirKhan]

What did you end up doing to mock extension methods. I need to mock app.UseMvc(); method in Configure method of the start up class but I cannot do so.

[gregsdennis]

I verified what the extension method did, which was to call a different method on the logger.

[stakx]

This will be fixed in the next release of Moq. The exception message will read:

Invalid verify on an extension method: l => l.Error(It.IsAny())