The integral part of any system development process is testing. Therefore, the Spring ecosystem offers the improved Spring Test and Spring Boot Test modules, which expand a list of additional functionalities for testing reactive Spring applications. In this way, Spring Test provides a WebTestClient for testing WebFlux-based web applications, and Spring Boot Test takes care of autoconfiguration for test suites using ordinary annotations.

In turn, to test Reactive Streams' Publisher, Project Reactor offers the Reactor-Test module, which—in combination with the Spring Test and Spring Boot Test modules—makes it possible to write complete verification suites for business logic implemented using Reactive Spring. All the details of reactive testing will be covered in Chapter 9, Testing the Reactive Application.