In this chapter, we focused on securing and testing the Spring Boot backend. Securing was first done with Spring Security. The frontend will be developed with React in upcoming chapters; therefore, we implemented JWT authentication, which is a lightweight authentication method suitable for our needs. We also covered the basics of testing a Spring Boot application. We used JUnit for unit testing and implemented test cases for JPA and RESTful web service authentication. In the next chapter, we will setup the environment and tools for the frontend development.