/mcs/class/System.ComponentModel.Composition/Tests/ComponentModelUnitTest/Microsoft/Internal/Collections/WeakReferenceCollectionTests.cs

// -----------------------------------------------------------------------

// Copyright (c) Microsoft Corporation.  All rights reserved.

// -----------------------------------------------------------------------

using System;

using System.Collections;

using System.Collections.Generic;

using System.UnitTesting;

using Microsoft.VisualStudio.TestTools.UnitTesting;



namespace Microsoft.Internal.Collections

{

    [TestClass]

    public class WeakReferenceCollectionTests

    {

        [TestMethod]

        public void Add_ObjectShouldGetCollected()

        {

            var obj = new object();

            var wrc = new WeakReferenceCollection<object>();



            wrc.Add(obj);



            var wr = new WeakReference(obj);

            obj = null;



            Assert.IsNotNull(wr.Target, "Object should NOT have been collected yet!");



            GC.Collect();

            GC.WaitForPendingFinalizers();



            Assert.IsNull(wr.Target, "Object should have been collected!");



            GC.KeepAlive(wrc);

        }



        [TestMethod]

        public void Remove_ObjectShouldGetRemoved()

        {

            var obj = new object();

            var wrc = new WeakReferenceCollection<object>();



            wrc.Add(obj);



            Assert.AreEqual(1, wrc.AliveItemsToList().Count, "Should have 1 item!");

            

            wrc.Remove(obj);



            Assert.AreEqual(0, wrc.AliveItemsToList().Count, "Should have 0 item!");

        }



        [TestMethod]

        public void AliveItemsToList_ShouldReturnAllItems()

        {

            var list = new object[] {new object(), new object(), new object()};

            var wrc = new WeakReferenceCollection<object>();



            foreach (object obj in list)

            {

                wrc.Add(obj);

            }



            Assert.AreEqual(list.Length, wrc.AliveItemsToList().Count, "Should have same number of items!");

        }



        [TestMethod]

        public void AliveItemsToList_ShouldReturnAllAliveItems()

        {

            var list = new object[] { new object(), new object(), new object() };

            var wrc = new WeakReferenceCollection<object>();



            var obj1 = new object();

            wrc.Add(obj1);



            foreach (object obj in list)

            {

                wrc.Add(obj);

            }



            var obj2 = new object();

            wrc.Add(obj2);



            Assert.AreEqual(list.Length + 2, wrc.AliveItemsToList().Count, "Should have same number of items!");



            obj1 = obj2 = null;



            GC.Collect();

            GC.WaitForPendingFinalizers();



            var aliveItems = wrc.AliveItemsToList();

            Assert.AreEqual(list.Length, aliveItems.Count, "Should have 2 less items!");



            Assert.AreEqual(list[0], aliveItems[0]);

            Assert.AreEqual(list[1], aliveItems[1]);

            Assert.AreEqual(list[2], aliveItems[2]);

        }



        [TestMethod]

        public void AliveItemsToList_ShouldReturnEmpty()

        {

            var wrc = new WeakReferenceCollection<object>();

            Assert.AreEqual(0, wrc.AliveItemsToList().Count, "Should have 0 items!");

        }

    }

}