How to assert two lists are not equivalent if in different order using Fluent Assertions

Question

Using Fluent Assertions we can assert that two collections are equal (in terms of property values) using something like:

list1.ShouldBeEquivalentTo(list2);

Assuming list1 and list2 are contain the same objects in any order, the assertion will be true.

If we want to assert the lists are in the exact order we can do something like this:

list1.ShouldBeEquivalentTo(list2, o => o.WithStrictOrdering());

I'm looking for something that assert false if the list contian the same objets in the wrong order but I can't find any.

What is the best way using Fluent Assertions?

PS - it a kind of academic curiosity, It might not even be that useful in reality :)

Answer 1

EDIT: Now that I understand what davy is asking for (see comment below) I updated my code to this solution. Although the syntax is similar, it is not a FluentAssertion extension, but with some manipulation it could be.

public static class IEnumerableAssertionExtensions
{
    public static void ShouldContainInWrongOrder<TSubject>(this IEnumerable<TSubject> source, IEnumerable<TSubject> expected)
    {
        var remaining = expected.ToList();
        var inOrder = true;
        foreach (var subject in source)
        {
            if (inOrder && !ReferenceEquals(subject, remaining[0]))
            {
                inOrder = false;
            }
            var s = subject;
            Execute.Verification.ForCondition(() => remaining.Remove(s)).FailWith("Expected item in the collection: {0}", subject.ToString());
        }

        Execute.Verification.ForCondition(() => remaining.Count == 0).FailWith(string.Format("{0} more item{1} than expected found in the list.", remaining.Count, ((remaining.Count == 1) ? string.Empty : "s")));
        Execute.Verification.ForCondition(() => !inOrder).FailWith("list items are ordered identically");
    }
}

[TestClass]
public class TestFoo
{
    class Thing
    {
        public int i;
    }

    [TestMethod]
    public void MyMethod()
    {
        var a1 = new Thing { i=0 };
        var a2 = new Thing { i=1 };
        var a3 = new Thing { i=2 };
        var a4 = new Thing { i=2 };
        var list1 = new List<Thing> { a1, a2, a3 };
        var list2 = new List<Thing> { a1, a2, a3 };
        var list3 = new List<Thing> { a3, a2, a1 };
        var list4 = new List<Thing> { a1, a2, a3, a4 };
        var list5 = new List<Thing> { a3, a2 };

        list1.ShouldContainInWrongOrder(list3); // Succeeds
        list1.ShouldContainInWrongOrder(list2); // Fails
        list1.ShouldContainInWrongOrder(list4); // Fails
        list1.ShouldContainInWrongOrder(list5); // Fails
    }
}