Testing in Spring Boot

The Spring Boot test starter package is automatically added to the build.gradle file by Spring Initializr when we create our project. The test starter dependency can be seen in the following snippet:

testImplementation 'org.springframework.boot:spring-boot-starter-test'

The Spring Boot test starter provides lots of handy libraries for testing, such as JUnit, Mockito, and AssertJ. Mockito is a mocking framework that is often used alongside testing frameworks like JUnit. AssertJ is a popular library for writing assertions in Java testing. In this book, we will use JUnit 5. The JUnit Jupiter module is part of JUnit 5 and provides annotations for more flexible testing.

If you take a look at your project structure, you’ll see that it already has its own package created for test classes:

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Figure 6.1: Test classes

By default, Spring Boot uses an in-memory database for testing. We are using MariaDB at this point in the...