HskellのMaybeクラスをC#で作ってみた。その３

HaskellのMaybeクラスをC#で作ってみた。その２で作成した
Maybeクラスの単体テストもNUnitを使って書いているので、
それも一緒に公開しておきます。

        [TestFixture]
        public class MaybeTest
        {
            [Test]
            public void MaybeNothingTest()
            {
                Maybe<int> nothing = Maybe<int>.Nothing;
                Assert.IsFalse(nothing.HasValue);
                Assert.Throws<InvalidOperationException>(delegate { int i = nothing.Value; });
            }

            [Test]
            public void MaybeFromTset()
            {
                DoMaybeFromTest((int)1);
                DoMaybeFromTest(DateTime.Now);
                DoMaybeFromTest(new InvalidOperationException());
                DoMaybeFromTest(new Action<int>(DoMaybeFromTest));
            }
            [Test]
            public void MaybeFromArgumentNullTset()
            {
                Assert.Throws<ArgumentNullException>(delegate { Maybe<InvalidOperationException>.Just(null); });
            }

            private static void DoMaybeFromTest<T>(T value)
            {
                Maybe<T> maybe = Maybe<T>.Just(value);
                Assert.IsTrue(maybe.HasValue);
                Assert.AreEqual(value, maybe.Value);
            }
            [Test]
            public void GetValueTest()
            {
                Maybe<int> nothing = Maybe<int>.Nothing;
                Assert.AreEqual(1, nothing.GetValue(1));

                Maybe<int> maybe = Maybe<int>.Just(20);
                Assert.AreEqual(20, maybe.GetValue(1));
            }
            [Test]
            public void EqualsTest()
            {
                Assert.IsTrue(Maybe<int>.Nothing.Equals(Maybe<int>.Nothing));
                Assert.IsTrue(Maybe<int>.Just(1).Equals(Maybe<int>.Just(1)));
                Assert.IsTrue(Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10)).Equals(Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10))));

                Assert.IsFalse(Maybe<int>.Nothing.Equals(null));
                Assert.IsFalse(Maybe<int>.Nothing.Equals(Maybe<int>.Just(1)));
                Assert.IsFalse(Maybe<int>.Just(19).Equals(Maybe<int>.Just(1)));
            }

            [Test]
            public void OperatorEqualsTest()
            {
                Assert.IsTrue(Maybe<int>.Nothing == Maybe<int>.Nothing);
                Assert.IsTrue(Maybe<int>.Just(1) == Maybe<int>.Just(1));
                Assert.IsTrue(Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10)) == Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10)));

                Assert.IsFalse(Maybe<int>.Nothing == null);
                Assert.IsFalse(null == Maybe<int>.Nothing);
                Assert.IsFalse(Maybe<int>.Nothing == Maybe<int>.Just(1));
                Assert.IsFalse(Maybe<int>.Just(19) == Maybe<int>.Just(1));
            }
            [Test]
            public void OperatorNotEqualsTest()
            {
                Assert.IsFalse(Maybe<int>.Nothing != Maybe<int>.Nothing);
                Assert.IsFalse(Maybe<int>.Just(1) != Maybe<int>.Just(1));
                Assert.IsFalse(Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10)) != Maybe<DateTime>.Just(new DateTime(2000, 10, 10, 10, 10, 10)));

                Assert.IsTrue(Maybe<int>.Nothing != null);
                Assert.IsTrue(null != Maybe<int>.Nothing);
                Assert.IsTrue(Maybe<int>.Nothing != Maybe<int>.Just(1));
                Assert.IsTrue(Maybe<int>.Just(19) != Maybe<int>.Just(1));
            }

            [Test]
            public void CastTest()
            {
                Maybe<Encoding> maybe = Maybe<Encoding>.Just(Encoding.UTF8);
                Assert.AreEqual(Encoding.UTF8, (Encoding)maybe);
            }
        }