How to use Mockito with HK2? - junit

Question

I'm using HK2 for dependency injection and want to replace a Singleton Object with a Mockito-mock in the context of a JUnit-Test.
The simplest setting would be as follows:
import javax.inject.Inject;
import org.jvnet.hk2.annotations.Service;
#Service
public class A {
#Inject
private B b;
public String test() {
return b.toString();
}
}
#Service
public class B {
public String toString()
{
return "B";
}
}
whereas the JUnit-Test stub is as follows:
import static org.junit.Assert.*;
import javax.inject.Inject;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.jvnet.hk2.testing.junit.HK2Runner;
import org.mockito.Mockito;
import org.mockito.junit.MockitoJUnitRunner;
#RunWith(MockitoJUnitRunner.class)
public class MockTest extends HK2Runner {
private B bMock = Mockito.mock(B.class);
#Inject
private A a;
#Test
public void test() {
Mockito.when(bMock.toString()).thenReturn("Mock");
assertEquals("Mocking worked", "Mock", a.test());
}
}
I want the Mock for B to be injected into A and not the real Object. How can I configure HK2 globally, such that for every instance of B the mock is used?
I already know that I could inject B locally into A by using injection via constructor.

Answer 1

Have you considered using a #Stub of B rather than a Mock?. To do that you can add #Contract onto the implementation of B:
#Service #Contract
public class B {
public String toString()
{
return "B";
}
}
and rather than using the mock use a #Stub:
public class MockTest extends HK2Runner {
#Inject
private A a;
#Test
public void test() {
assertEquals("Mocking worked", "Mock", a.test());
}
#Stub #Rank(1)
public static abstract class BStub extends B {
public String toString() {
return "Mock";
}
}
}
In order for this to work the hk2-metadata-generator should be in the classpath of your test during compilation so it can generate the stub. You put #Rank(1) on the stub to ensure it gets picked over the original B class.
Hope this helps!