Replace a bean by a mock in Helidon test - unit-testing

Question

I have a Helidon application and I would like to test (part of) it.
My test is annotated with #HelidonTest, and now I would like to replace one bean by a mock (and configure this mock, use all other beans as they are found, but with the mock injected).
I did figured out how to:
Replace one bean by a test implementation (separate class): By annotating the test implementation class with #Priority(1) and #Alternative and supply it by annotating the test with #AddBean(MyBeanTestImpl.class).
But I can not create a mock (with Mockito) as an individual class.
Produce a mock(MyBean.class): By creating a producer method and annotate it with #Produces:
But it clashes with the real bean and gives: "WELD-001409: Ambiguous dependencies for type..."
When I annotate it also with #Alternative it is simply ignored.
I can not annotate it with #Priority(1), because this annotation can only be applied to types and parameters.
Any idea how I can replace one bean by a mock?

Answer 1

I tried setter injection to manually inject mock beans.
Class under test
#ApplicationScoped
public class SomeService {
private ExternalService externalService;
#Inject
public void setExternalService(ExternalService externalService) {
this.externalService = externalService;
}
public String doSomething() {
return externalService.getData();
}
}
Test Class
#HelidonTest
class SomeServiceTest {
#Inject
private SomeService someService;
private ExternalService externalService;
#BeforeEach
void setUp() {
externalService = Mockito.mock(ExternalService.class);
someService.setExternalService(externalService);
}
#Test
void doSomething() {
Mockito.when(externalService.getData())
.thenReturn("Mock data");
String actual = someService.doSomething();
Assertions.assertEquals("Mock data", actual);
}
}
There are also methods to mock a whole bean by mocking the constructor as well. For that, we have to make use of #Observes annotation
#HelidonTest
public abstract class HelidonTestHelper {
private MockedConstruction<ExternalService> mockedConstruction;
void init(#Priority(1) #Observes #Initialized(ApplicationScoped.class) ContainerInitialized containerInitialized) {
mockedConstruction = Mockito.mockConstruction(ExternalService.class);
//mock common beans here. This will be executed once application scope is loaded.
}
void onStop(#Priority(1) #Observes #Destroyed(ApplicationScoped.class) ContainerShutdown containerShutdown) {
//do cleanup here if needed.
mockedConstruction.closeOnDemand();
}
}
Once the above is done, instead of helidon test, you can extend the helper class we created.
class SomeServiceTest extends HelidonTestHelper {
#Inject
private SomeService someService;
#Inject //this will be a mock
private ExternalService externalService;
#Test
void doSomething() {
Mockito.when(externalService.getData())
.thenReturn("Mock data");
String actual = someService.doSomething();
Assertions.assertEquals("Mock data", actual);
}
}