public void CombinedTest()
{
var c = new ExtensionCollection();
Assert.AreEqual(0, c.Count);
Assert.IsNull(c.Get <ExtensionCollectionTest>());
AssertEx.ThrowsArgumentException(() => c.Set(typeof(int), 1));
c.Set(this);
Assert.AreEqual(1, c.Count);
Assert.AreSame(this, c.Get <ExtensionCollectionTest>());
c.Lock();
AssertEx.Throws <InstanceIsLockedException>(() => c.Set(this));
var cc = (ExtensionCollection)c.Clone();
AssertEx.HasSameElements(c, cc);
var o = new object();
cc.Set(o);
Assert.AreEqual(2, cc.Count);
Assert.AreSame(this, cc.Get <ExtensionCollectionTest>());
Assert.AreSame(o, cc.Get <object>());
}