Engine engine = new Engine();
IntervalIteratingSystemSpy intervalSystemSpy = new IntervalIteratingSystemSpy();
ImmutableArray<Entity> entities = engine.getEntitiesFor(Family.all(IntervalComponentSpy.class).get());
ComponentMapper<IntervalComponentSpy> im = ComponentMapper.getFor(IntervalComponentSpy.class);
engine.addSystem(intervalSystemSpy);
for (int i = 0; i < 10; ++i) {
Entity entity = new Entity();
entity.add(new IntervalComponentSpy());
engine.addEntity(entity);