How do I setup this (Mock setup)

Question

I have the following test:

        var home = new DummyPageModel { Parent = null };
        var pageRepository = new Mock<IPageRepository>();
        pageRepository.Setup(x => x.SingleOrDefault<IPageModel>(page => page.Parent == null)).Returns(home);

but when I run this test I get a System.NotSupportedException : Expression page => (page.Parent == null) is not supported?

The implementation of SingleOrDefault looks like this:

    public T SingleOrDefault<T>(Func<T, bool> predicate) where T : IPageModel {
        return _documentSession.Query<T>().SingleOrDefault(predicate);
    }

Answer 1

Solved it like this:

pageRepository
    .Setup(
        x => x.SingleOrDefault(
            It.Is<Func<IPageModel, bool>>(page => home.Parent == null)
        )
    )
    .Returns(home);