Proposal: IsEquivalentTo matcher for IEnumerables ignoring order

Hey, I would like to propose a matcher similar to IsSameSequenceAs, but one that ignores ordering. Similar to CollectionAssert.AreEquivalent().

My initial idea was to implement a new IsEquivalentTo method that would have a required OrderByKey parameter which would be used to order both enumerables and then call IsSameSequenceAs internally for the matching.

Would like to know your opinions on it and if I should work on it.

Thanks in advance.

[thomaslevesque]

Yeah, I guess in typical unit tests you don’t work on very large lists… And what I said about using EqualityComparer<T>.Default doesn’t apply, unfortunately, because we won’t have a T (well, we will, but it will be the type of the collection, not the type of the items). So we’ll just have to use EqualityComparer<object>.Default instead.

[blairconrad]

We should just use the default equality comparer for the type (EqualityComparer<T>.Default) … And of course, we can let the user specify an equality comparer explicitly.

👍

I would probably go with an method that runs a match such as first.Count() == second.Count() && first.All(second.Contains)

That would be pretty inefficient (O(m*n))

I don’t think the efficiency is a big deal. Or at least we could be inefficient at first and see if it becomes one. I’m not against a more efficient solution, but if we don’t become convinced there’s a working and efficient solution, working inefficient is a reasonable tradeoff, IMO.