Be careful with Moq'ing out lists!

gistfile1.txt

        public class Thing
        {
            public virtual string DoThing(IList<string> args) { return "ONE"; }
        }

        [Fact]
        [Trait("00 Misc", "Reality Check")]
        public void Test()
        {
            var args = new List<string>() { "a", "b" };
            var result = "";

            var thing = new Thing();
            result = thing.DoThing(args); 
            Assert.True(result == "ONE");  // ONE - self-evident

            var moq = new Moq.Mock<Thing>();
            thing = moq.Object;
            moq.Setup(v => v.DoThing(args)).Returns("TWO");

            result = thing.DoThing(args);
            Assert.True(result == "TWO");  // TWO - yay, a valid  Moq
            
            args = new List<string>() { "a", "b" };
            result = thing.DoThing(args);
            Assert.True(result == "TWO"); // TWO - because list is the same

            args = new List<string>() { "c", "d" };
            result = thing.DoThing(args);
            Assert.True(result == null);      // NULL - the args is a different list

            args = new List<string>() { "c", "d","e" };
            result = thing.DoThing(args);
            Assert.True(result == null);      // NULL - definitely a different list

            moq.Setup(v => v.DoThing(It.IsAny<IList<string>>())).Returns("THREE");

            args = new List<string>() { "c", "d" };
            result = thing.DoThing(args);
            Assert.True(result == "THREE");      // THREE- any list of strings is good now!

            args = new List<string>();
            result = thing.DoThing(args);
            Assert.True(result == "THREE");      // THREE - even and empty list

            args = null;
            result = thing.DoThing(args);
            Assert.True(result == "THREE");      // THREE - even null
        }
    }