Cool use of predicate for Assertions

We recently switched from mbunit to nunit and I really missed mbunit’s Assert.ForAll method (which loops over all the elements in your enumeration and applies a predicate against each element).

Wanting to see how they did it I decompiled the mbunit source and found this cool implementation of how it’s done using predicates. Here is my code:

    public static class AssertExtensions
    {
        public static void ForAll<T>(IEnumerable<T> values, Predicate<T> predicate)
        {
            var failing = new List<T>();

            foreach (T value in values)
            {
                if (!predicate(value))
                    failing.Add(value);
            }

            if (failing.Count != 0)
                Assert.Fail();
        }
    }

Then you can use it like this:

var result = SomeRepository.SomeCollection();

AssertExtensions.ForAll(result, x => x.RemitToAddress == remitToAddress);
AssertExtensions.ForAll(result, x => x.VendorCode == "abc");

This is much nicer that having to loop over each of the elements yourself.