How do I unit test a C# function which returns a Func<something>?

Question

I have a class containing a method which returns a Result object which contains a property of type Func.

class Result {
   public Func<Result> NextAction { get; set; }
}

How do I write a unit test assertion regarding the content of this Func? The following obviously does not work, because the compiler generates two different methods for the lambda:

// Arrange
ListController controller = new ListController(domain);
// Act
Result actual = controller.DefaultAction();
// Assert
Func<Result> expected = () => new ProductsController(domain).ListAction();
Assert.That(actual.NextAction, Is.EqualTo(expected));

I'm guessing that I could do this by using expression trees instead, but... is there a way to avoid doing so? I'm using NUnit 2.5.

EDIT: There are no other identifying fields in the Result object. It is intended to be a way of invoking the next object/method based on a decision made in the current object/method.

Answer 1

Why not invoke the Func and compare the returned values?

var actualValue = actual.NextAction();
var expectedValue = expected();
Assert.That(actualValue, Is.EqualTo(expectedValue));

EDIT: I see that the Result class does not have any identity. I guess you have some other fields in the Result class that define the identity of the Result and can be used to determine if two results are equal.

Answer 2

I'm not aware of an easy way to look inside a lambda (other than using expression trees as you said) but it is possible to compare delegates if they're assigned a method group instead.

var result1 = new Result {
    NextAction = new ProductsController(domain).ListAction };
var result2 = new Result {
    NextAction = new ProductsController(domain).ListAction };

//objects are different
Assert.That(result1, Is.Not.EqualTo(result2));

//delegates are different
Assert.That(result1.NextAction, Is.Not.EqualTo(result2.NextAction));

//methods are the same
Assert.That(result1.NextAction.Method, Is.EqualTo(result2.NextAction.Method));

The above example does not work if you use lambdas since they are compiled to different methods.