CombiningEnums.cs

namespace ClassLibrary3
{
    using System.Diagnostics;

    using Xunit;

    public class CombiningEnums
    {
        [Fact]
        public void EnumsCanBeXored()
        {
            const Colors Green = Colors.Blue | Colors.Yellow;

            Green.Contains(Colors.Yellow);
            Green.Contains(Colors.Blue);
            Green.DoesNotContain(Colors.Red);
        }

    }

    public static class ColorAsserts
    {

        public static void Contains(this Colors color, Colors target)
        {
            Assert.Equal(color & target, target);
        }

        public static void DoesNotContain(this Colors color, Colors target)
        {
            Assert.NotEqual(color | target, target);
        }
    }
}