[TestClass]
public class GarbageCollectionTest
{
    [TestMethod]
    [Description("Asserts that an un-rooted object's finalizer will be called.")]
    public void GarbageCollectionTest01()
    {
        // Instantiate a spy to record that the Foo finalizer is called.
        var spy = new Spy();

        // Instantiate a new Foo.
        var foo = new Foo(spy);

        // Unroot foo.
        foo = null;

        // Force a collection.
        GC.Collect(0, GCCollectionMode.Forced, blocking: true);

        // Wait for all finalizers to have executed.
        GC.WaitForPendingFinalizers();

        // Assert that Foo's finalizer is called.
        // WARNING: This assertion fails in .NET Core 2.0, but works in .NET Core 1.1 and .NET Framework 4.7 and before.
        Assert.IsTrue(spy.FinalizerIsCalled);
    }

    private class Spy
    {
        public bool FinalizerIsCalled { get; set; }
    }

    private class Foo
    {
        ~Foo()
        {
            spy.FinalizerIsCalled = true;
        }

        public Foo(Spy spy)
        {
            this.spy = spy;
        }

        private readonly Spy spy;
    }
}