public void Remove()
        {
            TestDisposable[] o = new TestDisposable[4];
            for (int i = 0; i < o.Length; i++)
            {
                o[i] = new TestDisposable();
            }

            using (var disposer = new Disposables())
            {
                foreach (IDisposable d in o)
                {
                    disposer.Add(d);
                }
                disposer.RemoveAt(2);
            }
            for (int i = 0; i < o.Length; i++)
            {
                if (i == 2)
                {
                    Assert.IsFalse(o[i].IsDisposed);
                }
                else
                {
                    Assert.IsTrue(o[i].IsDisposed);
                }
            }
        }