I have a very basic game loop whose primary purpose is to check for updates & ch

Question

I have a very basic game loop whose primary purpose is to check for updates & changes to a list.

I have contemplated using event driven programming to replace the game loop/list idea with an ObservableCollection, however I just have this big cloud of doubt on event driven programming. I'm posing these questions to those with experience with event driven programming:

What are good ways to test & build an event driven programming design?

That is, how will I know that I cannot run into "a sequence of unfortunate events"? I want to avoid the events I didn't plan for.

Are there unit tests schemes to test event driven programming?
Because I have little reputation at the time of asking this question, I can't post more than two links: Observable collections are found at:

http://msdn.microsoft.com/en-us/library/ms668604.aspx

Explanation / Answer

I will leave aside the wisdom (or not) of this particuar design for a game engine, I will address the core concern about the testability of event-driven designs.

When you state

I want to avoid the events I didn't plan for.

I presume you mean a sequence that you did not plan for, like Create/Delete/Update instead of the expected Create/Update/Delete, where the former might try and update a non-existant object and therefore crash or otherwise fail.

The entire nature of event-driven programming has to actually presume a near-random order of events, and so effectively your pre- and post- conditions become very important. Since you cannot fully qualify the order of events, you need to be robust against accidental ordering. So long as your Delete leaves no stray pointers, then a delayed Update should unambiguously fail, or at least have some well-defined behavior.

As far as unit-testing goes, most of the common suggestions would still apply. Generate test cases for various boundary conditions, as well as common cases to try and achieve appropriate coverage and interaction testing.

Perhaps in your game, I should be able to PickUp an item, which would add it to my inventory. If I attempt to PickUp an item, which was just destroyed for some reason (perhaps an ogre stepped on it), I should not somehow get an undamaged object due to a race condition. Either I got the object before it was crushed, or it is now gone, but nothing inbetween. If each event is atomic with respect to game state, then you won't get a partial object someplace it should not be.

Good Luck

Related Questions

Navigate

• Browse (All)
• Browse I
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.