Verify method has been called with IEnumerable containing 'x' elements with Moq

Question

I have a repository with an Add method that takes an IEnumerable as parameter:

public void Add<T>(T item) where T : class, new(){}

In a unittest I want to verify that this method is called with an IEnumerable that contains exactly the same amount of elements as another IEnumerable

[Test]
public void InvoicesAreGeneratedForAllStudents()
{
    var students = StudentStub.GetStudents();
    session.Setup(x => x.All<Student>()).Returns(students.AsQueryable());

    service.GenerateInvoices(Payments.Jaar, DateTime.Now); 

    session.Verify(x => x.Add(It.Is<IEnumerable<Invoice>>(
        invoices => invoices.Count() == students.Count())));
 }

Result of the unit test:

Moq.MockException : 
Expected invocation on the mock at least once, but was never performed: 

x => x.Add<Invoice>(It.Is<IEnumerable`1>(i => i.Count<Invoice>() == 10))

No setups configured.

What am I doing wrong?

Ciaran · Accepted Answer · 2011-06-02T15:33:18.193

From your code example you haven't set up the x => x.Add on the Moq

session.Setup(x => x.Add(It.IsAny<IEnumerable>());

Unless the Setup for x.All is meant to be x.Add? If so, you need to match the Verify and Setup exactly - a good way to do that is to extract it to a common method that returns an Expression.

EDIT: Added a sample, I have changed the signature of Add as I can't see how you could pass a collection otherwise.

[TestClass]
public class UnitTest1
{
    [TestMethod]
    public void TestMethod1()
    {
        Mock<Boo> moqBoo = new Mock<Boo>();
        moqBoo.Setup(IEnumerableHasExpectedNumberOfElements(10));

        // ACT

        moqBoo.Verify(IEnumerableHasExpectedNumberOfElements(10));
    }

    private static Expression<Action<Boo>> IEnumerableHasExpectedNumberOfElements(int expectedNumberOfElements)
    {
        return b => b.Add(It.Is<IEnumerable<Invoice>>(ie => ie.Count() == expectedNumberOfElements));
    }
}

public class Boo
{
    public void Add<T>(IEnumerable<T> item) where T : class, new()
    {
    }
}

public class Invoice
{

}

Also, a good way to debug these things is to set your Mock up with MockBehavior.Strict and then you'll be informed by the invoked code what you need to configure.

Verify method has been called with IEnumerable containing 'x' elements with Moq

1 Answers1