SpringRunner vs SpringBootTest
@RunWith(SpringRunner.class) : You need this annotation to just enable spring boot features like
@MockBean etc.. during junit testing
is used to provide a bridge between Spring Boot test features and JUnit. Whenever we are using any Spring Boot testing features in our JUnit tests, this annotation will be required.
@SpringBootTest : This annotation is used to load complete application context for end to end integration testing
The @SpringBootTest annotation can be used when we need to bootstrap the entire container. The annotation works by creating the ApplicationContext that will be utilized in our tests.
Here is the article with clear examples on both scenarios Baeldung
@RunWith is an old annotation from JUnit 4 to use test runners. If you're using JUnit 5 (Jupiter), you should use @ExtendWith to use JUnit extensions
"If you are using JUnit 4, don’t forget to also add @RunWith(SpringRunner.class) to your test, otherwise the annotations will be ignored. If you are using JUnit 5, there’s no need to add the equivalent @ExtendWith(SpringExtension.class) as @SpringBootTest and the other @…Test annotations are already annotated with it.