public void TestChangingSceneGraphForEntity()
{
var entity = new MockEntity(0);
entity.Initialize();
var root1 = new SceneGraphRoot();
var root2 = new SceneGraphRoot();
root1.AddAsync(entity);
entity.Parent.Should().Be(root1);
new Action(() => root1.AddAsync(entity)).Should().Throw <NotSupportedException>();
root1.RemoveAsync(entity);
entity.Parent.Should().Be(root1, "because RemoveScheduled will only be called in the next update");
root1.Update(new GameTime());
entity.Parent.Should().BeNull("because update now removed the entity from the scene");
root2.AddAsync(entity);
entity.Parent.Should().Be(root2);
root1.IsRegistered(entity).Should().BeFalse("because it will only be registered in the update call");
new Action(() => entity.ChangeParent(root1)).Should().Throw <NotSupportedException>();
// call update so entity is actually registered with the root2
root2.Update(new GameTime());
// only now is the alternative method possible
entity.ChangeParent(root1);
entity.Parent.Should().Be(root1);
}