NUnit Collection Equivalence Extension Methods

gistfile1.cs

    public static class NUnitExtensions
    {
        public static CollectionItemsEqualConstraint Using<T>(this CollectionEquivalentConstraint constraint,
            Func<T, T, bool> expression)
        {
            return constraint.Using(new PredicateComparison<T>(expression));
        }

        public static CollectionItemsEqualConstraint Using<TExpected, TActual>(this CollectionEquivalentConstraint constraint,
            Func<TExpected, TActual, bool> expression)
        {
            return constraint.Using(new PredicateComparison<TExpected, TActual>(expression));
        }
    }

public class PredicateComparison<T> : IComparer<T>
{
	private readonly Func<T, T, bool> _comparison;

	public int Compare(T x, T y)
	{
		if (_comparison.Invoke(x, y))
		{
			return 0;
		}
		return -1;
	}

	public PredicateComparison(Func<T, T, bool> comparison)
	{
		_comparison = comparison;
	}
}


    public class PredicateComparison<TExpected, TActual> : IComparer
    {
        private readonly Func<TExpected, TActual, bool> _func;

        public int Compare(object x, object y)
        {
            var expected = (TExpected)x;
            var actual = (TActual)y;

            if (_func(expected, actual))
                return 0;

            return -1;
        }

        public PredicateComparison(Func<TExpected, TActual, bool> func)
        {
            _func = func;
        }
    }

Lets you write

Assert.That(actualCollection, Is.EquivalentTo(expectedCollection)
    .Using<T>((x, y) => x.Id == y.Id));

Or: Assert.That(actualCollection, Is.EquivalentTo(expectedCollection)
.Using<TExpected, TActual>((x, y) => x.Id == y.SomeOtherProperty));