I caught a whiff of a smell eminating from one of my tests, in a scenario akin to the following:

[TestFixture]
public void CarPresenterTests{

    [Test]
    public void Throws_If_Cars_Wheels_Collection_Is_Null(){
         IEnumerable<Wheels> wheels = null;
         var car = new Car(wheels);
         Assert.That(
         ()=>new CarPresenter(car),
         Throws.InstanceOf<ArgumentException>()
         .With.Message.EqualTo("Can't create if cars wheels is null));
    }
}

public class CarPresenter{
    public CarPresenter(Car car)
    {
        if(car.Wheels == null)
            throw new ArgumentException("Can't create if cars wheels is null);
        _car = car;
        _car.Wheels.Rolling += WheelsRollingHandler;
    }
}

I was struggling to describe what the problem is except that it seems wrong that a CarPresenter should attempt to dictate to a Car whether or not it's Wheels are initialised correctly.

I wondered what pointers people here might give me?