A set of regression tests for lazy

lazy_regression.cs

using System;
using Microsoft.VisualStudio.TestTools.UnitTesting;
using System.Threading;
using System.Reflection;

namespace LazyTest
{
    [TestClass]
    public class LazyRegressionTests
    {
        class MyException
            : Exception
        {
            public int Value { get; }

            public MyException(int value)
            {
                Value = value;
            }
        }

        public class Simple
        {
            public int Value { get; }

            public Simple(int value)
            {
                Value = value;
            }

            public Simple()
            {
                Value = 42;
            }
        }

        public void SimpleInt(Lazy<int> lazy)
        {
            Assert.IsFalse(lazy.IsValueCreated);
            Assert.AreEqual(lazy.Value, 42);
            Assert.IsTrue(lazy.IsValueCreated);
        }

        [TestMethod]
        public void SimpleInteger()
        {
            SimpleInt(new Lazy<int>(() => 42));
            SimpleInt(new Lazy<int>(() => 42, true));
            SimpleInt(new Lazy<int>(() => 42, false));
            SimpleInt(new Lazy<int>(() => 42, LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleInt(new Lazy<int>(() => 42, LazyThreadSafetyMode.None));
            SimpleInt(new Lazy<int>(() => 42, LazyThreadSafetyMode.PublicationOnly));
        }

        public void SimpleObject(Lazy<Simple> lazy)
        {
            Assert.IsFalse(lazy.IsValueCreated);
            Assert.AreEqual(lazy.Value.Value, 42);
            Assert.IsTrue(lazy.IsValueCreated);
        }

        [TestMethod]
        public void SimpleObject()
        {
            SimpleObject(new Lazy<Simple>());
            SimpleObject(new Lazy<Simple>(true));
            SimpleObject(new Lazy<Simple>(false));
            SimpleObject(new Lazy<Simple>(LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleObject(new Lazy<Simple>(LazyThreadSafetyMode.None));
            SimpleObject(new Lazy<Simple>(LazyThreadSafetyMode.PublicationOnly));
            SimpleObject(new Lazy<Simple>(() => new Simple(42)));
            SimpleObject(new Lazy<Simple>(() => new Simple(42), true));
            SimpleObject(new Lazy<Simple>(() => new Simple(42), false));
            SimpleObject(new Lazy<Simple>(() => new Simple(42), LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleObject(new Lazy<Simple>(() => new Simple(42), LazyThreadSafetyMode.None));
            SimpleObject(new Lazy<Simple>(() => new Simple(42), LazyThreadSafetyMode.PublicationOnly));
        }

        public void SimpleIntException(Lazy<int> lazy)
        {
            MyException e = null;
            try
            {
                var _ = lazy.Value;
            }
            catch(MyException thrown)
            {
                e = thrown;
            }
            Assert.IsNotNull(e);
            Assert.AreEqual(e.Value, 99);
        }

        [TestMethod]
        [ExpectedException(typeof(MyException), "")]
        public void SimpleIntegerException()
        {
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }));
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }, true));
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }, false));
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.None));
            SimpleInt(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.PublicationOnly));
        }

        public class SimpleException
        {
            public SimpleException() : this(99) { }

            public SimpleException(int value)
            {
                throw new MyException(value);
            }
        }

        public void SimpleObjectException(Lazy<SimpleException> lazy)
        {
            TargetInvocationException e = null;
            try
            {
                var _ = lazy.Value;
            }
            catch (TargetInvocationException ex)
            {
                e = ex;
            }
            Assert.IsNotNull(e);
        }

        [TestMethod]
        [ExpectedException(typeof(MyException), "")]
        public void SimpleObjectException()
        {
            SimpleObjectException(new Lazy<SimpleException>());
            SimpleObjectException(new Lazy<SimpleException>(true));
            SimpleObjectException(new Lazy<SimpleException>(false));
            SimpleObjectException(new Lazy<SimpleException>(LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleObjectException(new Lazy<SimpleException>(LazyThreadSafetyMode.None));
            SimpleObjectException(new Lazy<SimpleException>(LazyThreadSafetyMode.PublicationOnly));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99)));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99), true));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99), false));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.ExecutionAndPublication));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.None));
            SimpleObjectException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.PublicationOnly));
        }

        public void SameException<T>(Lazy<T> x)
        {
            Exception first = null;
            try
            {
                var _ = x.Value;
            }
            catch (Exception thrown1)
            {
                first = thrown1;
            }
            Assert.IsNotNull(first);

            try
            {
                var _ = x.Value;
            }
            catch (MyException thrown2)
            {
                Assert.AreSame(first, thrown2);
            }
        }

        public void DifferentException<T>(Lazy<T> x)
        {
            Exception first = null;
            try
            {
                var _ = x.Value;
            }
            catch (Exception thrown1)
            {
                first = thrown1;
            }
            Assert.IsNotNull(first);

            Exception second = null;
            try
            {
                var _ = x.Value;
            }
            catch (Exception thrown2)
            {
                second = thrown2;
            }
            Assert.IsNotNull(second);

            Assert.AreNotEqual(first, second);
        }

        [TestMethod]
        public void SameException()
        {
            SameException(new Lazy<int>(() => { throw new MyException(99); }));
            SameException(new Lazy<int>(() => { throw new MyException(99); }, true));
            SameException(new Lazy<int>(() => { throw new MyException(99); }, false));
            SameException(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.ExecutionAndPublication));
            SameException(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.None));
            DifferentException(new Lazy<int>(() => { throw new MyException(99); }, LazyThreadSafetyMode.PublicationOnly));

            DifferentException(new Lazy<SimpleException>());
            DifferentException(new Lazy<SimpleException>(true));
            DifferentException(new Lazy<SimpleException>(false));
            DifferentException(new Lazy<SimpleException>(LazyThreadSafetyMode.ExecutionAndPublication));
            DifferentException(new Lazy<SimpleException>(LazyThreadSafetyMode.None));
            DifferentException(new Lazy<SimpleException>(LazyThreadSafetyMode.PublicationOnly));
            SameException(new Lazy<SimpleException>(() => new SimpleException(99)));
            SameException(new Lazy<SimpleException>(() => new SimpleException(99), true));
            SameException(new Lazy<SimpleException>(() => new SimpleException(99), false));
            SameException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.ExecutionAndPublication));
            SameException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.None));
            DifferentException(new Lazy<SimpleException>(() => new SimpleException(99), LazyThreadSafetyMode.PublicationOnly));
        }

        public void MultipleInt(Lazy<int> lazy, ref int counter, int expected)
        {
            counter = 0;
            var result = 0;
            for (var i=0; i < 10; ++i)
            {
                try { result = lazy.Value; } catch (Exception) { }
            }
            Assert.AreEqual(result, expected);
        }

        [TestMethod]
        public void Multiple()
        {
            var counter = 0;
            var f = new Func<int>(() => { if (++counter < 5) throw new MyException(42); else return counter; });

            MultipleInt(new Lazy<int>(f), ref counter, 0);
            MultipleInt(new Lazy<int>(f, true), ref counter, 0);
            MultipleInt(new Lazy<int>(f, false), ref counter, 0);
            MultipleInt(new Lazy<int>(f, LazyThreadSafetyMode.ExecutionAndPublication), ref counter, 0);
            MultipleInt(new Lazy<int>(f, LazyThreadSafetyMode.None), ref counter, 0);
            MultipleInt(new Lazy<int>(f, LazyThreadSafetyMode.PublicationOnly), ref counter, 5);
        }

        public void MultipleObject(Lazy<Simple> lazy, ref int counter, int? expected)
        {
            counter = 0;
            var result = default(Simple);
            for (var i = 0; i < 10; ++i)
            {
                try { result = lazy.Value; } catch (Exception) { }
            }
            if (expected == null)
                Assert.IsNull(result);
            else
                Assert.AreEqual(result.Value, expected.Value);
        }

        [TestMethod]
        public void MultipleObject()
        {
            var counter = 0;
            var f = new Func<Simple>(() => { if (++counter < 5) throw new MyException(42); else return new Simple(counter); });

            MultipleObject(new Lazy<Simple>(f), ref counter, null);
            MultipleObject(new Lazy<Simple>(f, true), ref counter, null);
            MultipleObject(new Lazy<Simple>(f, false), ref counter, null);
            MultipleObject(new Lazy<Simple>(f, LazyThreadSafetyMode.ExecutionAndPublication), ref counter, null);
            MultipleObject(new Lazy<Simple>(f, LazyThreadSafetyMode.None), ref counter, null);
            MultipleObject(new Lazy<Simple>(f, LazyThreadSafetyMode.PublicationOnly), ref counter, 5);
        }

        class SimpleConstructor
        {
            public static int counter = 0;
            public static int getValue()
            {
                if (++counter < 5)
                    throw new MyException(42);
                else
                    return counter;
            }

            public int Value { get; }

            public SimpleConstructor()
            {
                Value = getValue(); 
            }
        }

        void MultipleObject(Lazy<SimpleConstructor> lazy, int? expected)
        {
            SimpleConstructor.counter = 0;
            var result = default(SimpleConstructor);
            for (var i = 0; i < 10; ++i)
            {
                try { result = lazy.Value; } catch (Exception) { }
            }
            if (expected == null)
                Assert.IsNull(result);
            else
                Assert.AreEqual(result.Value, expected.Value);
        }

        [TestMethod]
        public void MultipleConstructorObject()
        {
            MultipleObject(new Lazy<SimpleConstructor>(), 5);
            MultipleObject(new Lazy<SimpleConstructor>(true), 5);
            MultipleObject(new Lazy<SimpleConstructor>(false), 5);
            MultipleObject(new Lazy<SimpleConstructor>(LazyThreadSafetyMode.ExecutionAndPublication), 5);
            MultipleObject(new Lazy<SimpleConstructor>(LazyThreadSafetyMode.None), 5);
            MultipleObject(new Lazy<SimpleConstructor>(LazyThreadSafetyMode.PublicationOnly), 5);
        }

        public void CheckForInvalidOperationException<T>(ref Lazy<T> x, Lazy<T> lazy)
        {
            x = lazy;

            var correct = false;
            try
            {
                var _ = lazy.Value;
            }
            catch (InvalidOperationException)
            {
                correct = true;
            }
            Assert.IsTrue(correct);
        }

        [TestMethod]
        public void Recursion()
        {
            Lazy<int> x = null;
            Func<int> f = () => x.Value;

            CheckForInvalidOperationException(ref x, new Lazy<int>(f));
            CheckForInvalidOperationException(ref x, new Lazy<int>(f, true));
            CheckForInvalidOperationException(ref x, new Lazy<int>(f, false));
            CheckForInvalidOperationException(ref x, new Lazy<int>(f, LazyThreadSafetyMode.ExecutionAndPublication));
            CheckForInvalidOperationException(ref x, new Lazy<int>(f, LazyThreadSafetyMode.None));

            // this just hangs in current implementation
            // CheckForInvalidOperationException(ref x, new Lazy<int>(f, LazyThreadSafetyMode.PublicationOnly));
        }
    }
}