Spring Boot Integration Test Wiring for all projects with tests developed in Kotlin

Rules for how dependencies get injected and mocked in this project's integration tests. Apply these whenever creating a new integration test class or reviewing/editing an existing one.

1. Constructor injection only — no field injection (only for Kotlin files .kt)

Integration test classes must wire their dependencies through the constructor, never through @Autowired fields. This skill applies to all modules and submodules of the whole project. This means that all tests made in Kotlin are a subject of this skill. Only Kotlin files, the ones with the .kt extension should be subject to this change. No other files should be affected.

Do:

@SpringBootTest
class JeorgActionAOPLauncherExtAOPTest @Autowired constructor(
  private val bonitoCatcher: BonitoCatcher,
  private val codCatcher: CodCatcher
) {
}

Don't:

@SpringBootTest
class JeorgActionAOPLauncherExtAOPTest() {

    @Autowired
    lateinit var bonitoCatcher: BonitoCatcher

    @Autowired
    lateinit var codCatcher: CodCatcher;
}

Notes:

• For every file with extension .kt that ends in IT or Test, make sure that if they need @Autowire annotated fields or params, that they get injected via the mentioned above @Autowired constructor pattern.
• JUnit 5 + Spring's TestConstructor support allows constructor injection in test classes the same way it works in production beans. If the project hasn't set spring.test.constructor.autowire.mode=all in application-test.properties (or via @TestConstructor(autowireMode = ALL)), the constructor still needs an explicit @Autowired annotation as shown above — include it only in the constructor and remove it from the fields, or the injected params.
• Keep injected fields private val.
• If a test only needs one or two collaborators, still use the constructor — don't fall back to field injection "just for this one."
• If the @Autowired constructor pattern is already in use, make sure that all injected params are private val, but also remove @Autowire if they have it.
• For all beans using any of the annotations @MockitoBean, @MockBean, @SpyBean, @MockkBean, @MockkSpyBean, or others, and injected with lateinit, please put them with the correct annotation in the constructor as well

2. Replace initMocks with OpenMocks

Example 1

When finding this:

initMocks(testRestTemplate)

Replace with:

openMocks(testRestTemplate)

Also replace imports from import org.mockito.MockitoAnnotations.initMocks to import org.mockito.MockitoAnnotations.openMocks

3. Migrate @MockBean annotations

The annotation @MockBean is deprecated and its usage needs to be replaced by @MockitoBean The annotation @SpyBean is deprecated and its usage needs to be replaced by @MockitoSpyBean The above annotations should be updated in the same way following the examples bellow.

Example 1

On a class level, replace this:

@MockBean(Planet.class)
private MyService myService;

with this:

@MockitoBean(types = Planet.class)
private MyService myService;

Example 2

Replace also the usages of import org.springframework.boot.test.mock.mockito.MockBean; with import org.springframework.test.context.bean.override.mockito.MockitoBean;

Example 3

The beans that are declared are like this:

@MockBean
private BankCompanyBankRepository bankCompanyBankRepository;

should be replaced to something like:

@MockitoBean
private BankCompanyBankRepository bankCompanyBankRepository;

4. MockMvc test upgrade for Sprin Boot 4.0.0

Please add:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-webmvc-test</artifactId>
    <scope>test</scope>
</dependency>

as a dependency for projects that use WebMvcTest

Replace the import: import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest to org.springframework.boot.webmvc.test.autoconfigure.WebMvcTest

5. MockKBean uses different syntax in recent MockK versions

The syntax is slightly changed in the latest Spring MocK versions.

Example 1

Changes in MockKBean

Replace @MockkBean(classes = [DataSource::class]) with @MockkBean(types = [DataSource::class])

6. There should be no integration/unit/other tests creating entities with an assigned id

Creating entities via JPA should assume the usage of an ID autogeneration engine. It could be a sequence, or something else, like a counter, entity, or any other strategy If creating an entity like this, somehow works and is used in the test, the test should be updated so that it does not use a fixed ID on the entity creation and persistence to the database.

Updates and other CRUD methods should be left as is. Only on creation should the above be considered.

7. Test class checklist

Before submitting/reviewing an integration test class, confirm:

• All Spring-managed dependencies come in through the constructor
• Constructor is annotated @Autowired (unless project-wide TestConstructor autowire mode is configured)
• No @Autowired on fields
• Use the new Spring configuration for security
• New Spring versions don't use AntPathRequestMatcher anymore. Make sure none is used
• No @MockBean or @SpyBean annotations are used. Use @MockitoBean or @MockitoSpyBean instead.
• No @MockkBean(classes = type of declarations left
• No more usages of import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest