Unit tests for a simple composite
If you rename these:


    var changedClaim1 = CreateAnyChangedClaim();
    var changedClaim2 = CreateAnyChangedClaim();
    var changedClaim3 = CreateAnyChangedClaim();
    var changedClaim4 = CreateAnyChangedClaim();



Like this:

    var service1changedClaim1 = CreateAnyChangedClaim();
    var service1changedClaim2 = CreateAnyChangedClaim();
    var service2changedClaim1 = CreateAnyChangedClaim();
    var service2changedClaim1 = CreateAnyChangedClaim();


Then it will be more obvious that these will be used in two different services. These names will carry more meaning than just an arbitrary list of IChangedClaim objects.



What is "sut" ? A more meaningful name would be better.



In this assert:


    Assert.That(result, Is.EqualTo(expectedResult), "result");



The comment message is not very useful.
Either make it something more meaningful, or delete it.