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. 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.