Is there a .NET Testing framework that can assert a collection contains elements based on an expression?

Question

I'm trying to test that a certain function I'm building will add objects to a collection when supplied with a collection of Ids.

My test looks something like this:

var someClass = new SomeClass();
var someIds = new List<Guid> { Guid.NewGuid(), Guid.NewGuid(), Guid.NewGuid() };

someClass.AddIds(someIds);

Asset.That(someClass.IdsInClass, List.???);

The property IdsInClass is actually an IList and for the sake of argument lets say that it looks something like this:

public class SomeOtherClass
{
    public Guid Id { get; set; }
    public SomeClass Parent { get; set; }
    //other properties we don't care about for this test
}

I want to make sure that all the ids I made in my test are being added to someClass.IdsInClass

What is the best way to do that?

I was thinking maybe an expression would work like so:

Assert.That(someClass.IdsInClass, 
    List<SomeOtherClass>.HasAll(x => someIds.Contains(x.Id));

But I don't know if anything like that exists.

Answer 1

You could use LINQ expressions that resolve to a boolean. For example, I write code similar to the following with NUnit tests:

List<string> items = ...
Assert.That(items.All(item => item.Contains("x")))

Does that help?

Answer 2

I would use Linq's All...

Assert.True( someIds.All( id => someClass.IdsInClass.Contains( id ) ) );

Answer 3

There is a dedicated assertion in Gallio/MbUnit for that specific test case:

Assert.ForAll(someIds, id => someClass.IdsInClass.Contains(id));

The benefit is that Gallio tells which particular elements of sequence are failing (if any). That's certainly better than just getting a generic message indicating that the expression evaluated by Assert.IsTrue is just not true.