It's very common to hear about issues, but if an app doesn't have any important issue, it doesn't mean that it is working fine. Imagine that you have a program that has a memory leak, presumably you won't find any problem using it for 10 minutes. However, a user may find it after using it for a few days. Don't think that this sort of thing is impossible; remember that iOS apps don't terminate, so if you do have memory leaks, it will be kept until your app blows up.

Performance is another important, common topic. What if your app looks okay, but it gets slower with the passing of time? We, therefore, have to be aware of this problem. This kind of test is called profiling and Xcode comes with a very good tool for realizing this operation, which is called Instruments.

In this instance, we will profile our app to visualize the amount of energy wasted by our app and, of course, let's try to reduce it.