How to write a proper test case for controller, service and Dao in spirng boot using junit 5?

Question

How to write a proper test case for controller, service and Dao in spring boot using junit 5 with clear explanation

Answer 1

Spring Boot has a concept of test slices. This type of test configuration will setup only a part of your application and thus making tests:

• less likely to break on not-related change,
• faster in comparison to configuring all application services (using @SpringBootTest annotation).

For example @JsonTest slice will configure ObjectMapper (and some test utilities for JSON) in the same way as it would happen on production.

Anyway, to your mentioned types:

• DAO - use @DataJpaTest slice - it will configure Hibernate with in-memory database and load all your entities and repositories.
• Controllers - use @WebMvcTest(YourController.class) slice - it will load only configuration for Spring MVC, advices and your controller. You will be responsible to deal with dependencies of that controller.
• Services - pretty much depends on what is your service doing. I prefer using slices also for services depending on Spring-configured beans but your test can also be a very simple standard [j]unit test with all dependencies mocked away. - Depending on the compromise you want to make.

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This does not change with the fifth version of junit. The only difference is that you no longer need to annotate your tests with @RunWith(SpringRunner.class).