What we've already covered are so-called functional tests. Their aim is to check whether the system under test fulfills the functional requirements. But there are also other types of requirements besides functional ones that we may want to control. Some of them are as follows:
- Performance: Your application may behave according to requirements in terms of functionality but still be unusable for end users due to weak performance. We will focus more on improving performance in Chapter 11, Performance.
- Endurance: Even if your system can be really performant, it doesn't mean it can survive a continuously high workload. And when it does, can it survive some of the malfunctionings of the components? When we embrace the idea that every piece of software is vulnerable and may break at any given moment, we start designing systems that can be failure-resistant. This is a concept that the Erlang ecosystem embraces, but the concept itself is not limited...
