stFrame, TestObjectInstance);

      const testObject = collection.getObjectInstanceAt(scopedId, 20);
      assert.instanceOf(testObject, tr.model.ObjectInstance);
      assert.instanceOf(testObject, TestObjectInstance);
    } finally {
      tr.model.ObjectInstance.subTypes.unregister(TestObjectInstance);
    }
  });

  test('twoSnapshots', function() {
    const collection = new tr.model.ObjectCollection({});
    const scopedId = new tr.model.ScopedId('ptr', '0x1000');
    collection.idWasCreated(
       