Performance testing

If contract testing allows you to ensure that your API behavior is consistent over time, performance testing gives you the information you need while tuning your API to deliver the best possible consumer experience. In Chapter 2, you learned that reliability and performance are fundamental to a positive API user experience. In particular, having an API that responds well under growing load situations is critical. As you’re seeking success for your API product, you want the number of consumers to grow, and your API has to stay performant.

Actually, both scalability—the ability to stay performant even with increasing levels of usage—and responsiveness are the two things that you verify during a performance test. Scalability can be tested by increasing the usage load in a controlled fashion and seeing how the response behavior changes. In each step of increasing load, you test the API responsiveness and measure how well it can process the same...