Question

We have a bunch of classes that listen for events from the server and then respond to them. For example:

class EventManager {
    private Set<Event> cache = new HashSet<Event>();

    private EventListener eventListener = new EventListener() {
        void onEvent(Event e) {
          if (e instanceof MyEvent || e instanceof YourEvent) {
            handleEvent(e);
          }  
        }
    }

    public EventManager(ServerCommunication serverComm) {
        serverComm.addListener(eventListener);
    }

    private handleEvent(Event e) {
        // handle the event...
        // ...
        cache.add(cache);
        // ...
    }
}

Here’s a made-up example of the kind of thing we are doing. Here are the problems I see:

1. I’d like to test handleEvent to make sure it’s doing what it is supposed to but I can’t because it’s private.
2. I’d also like to check that something got added to the cache too but that also seems difficult since cache is a private member and I don’t want to add a needless getter method.
3. I’d also like to test the code inside the anonymous class’s onEvent method.

For now, what I did was move all logic from the anonymous class to the handleEvent method, and I made handleEvent package private (my unit test is in the same package). I’m not checking the contents of the cache although I want to.

Does anyone have any suggestion for a better design that is more testable?

Answer 1

I would probably extract a EventCache component. You can replace this for your test with an implementation that counts the cached events or records whatever is of interest.

I probably would not change the visibility of handleEvent. You could implement a ServerCommunication that just raises the event from the test case.