How can I write a unit test to determine whether an object can be garbage collected?

Question

In relation to my previous question, I need to check whether a component that will be instantiated by Castle Windsor, can be garbage collected after my code has finished using it. I have tried the suggestion in the answers from the previous question, but it does not seem to work as expected, at least for my code. So I would like to write a unit test that tests whether a specific object instance can be garbage collected after some of my code has run.

Is that possible to do in a reliable way ?

EDIT

I currently have the following test based on Paul Stovell's answer, which succeeds:

     [TestMethod]     public void ReleaseTest()     {         WindsorContainer container = new WindsorContainer();         container.Kernel.ReleasePolicy = new NoTrackingReleasePolicy();         container.AddComponentWithLifestyle<ReleaseTester>(LifestyleType.Transient);         Assert.AreEqual(0, ReleaseTester.refCount);         var weakRef = new WeakReference(container.Resolve<ReleaseTester>());         Assert.AreEqual(1, ReleaseTester.refCount);         GC.Collect();         GC.WaitForPendingFinalizers();         Assert.AreEqual(0, ReleaseTester.refCount, "Component not released");     }      private class ReleaseTester     {         public static int refCount = 0;          public ReleaseTester()         {             refCount++;         }          ~ReleaseTester()         {             refCount--;         }     } 

Am I right assuming that, based on the test above, I can conclude that Windsor will not leak memory when using the NoTrackingReleasePolicy ?

Answer 1

This is what I normally do:

[Test] public void MyTest()  {     WeakReference reference;     new Action(() =>      {         var service = new Service();         // Do things with service that might cause a memory leak...          reference = new WeakReference(service, true);     })();      // Service should have gone out of scope about now,      // so the garbage collector can clean it up     GC.Collect();     GC.WaitForPendingFinalizers();      Assert.IsNull(reference.Target); } 

NB: There are very, very few times where you should call GC.Collect() in a production application. But testing for leaks is one example of where it's appropriate.

Answer 2

Perhaps you could hold a WeakReference to it and then check to see that it no longer alive (i.e., !IsAlive) after the tests have completed.