Mock an Interface with Mockito return a NullPointerException - interface

Question

I m trying create unit tests for one project.I m facing a problem because when I try control the result of an interface(mock). When the code get the Interface variable that return a NullPointerException.
Firstly I tried #Override the method in my test class (ClassA), but it don't work. After that I tried mock the interface object and control the comportment with Mockito.When().tehnReturn();
I will put here my code, I read some solutions but none works.
My Interface:
#FunctionalInterface
public interface Interface {
UpdateXResponse process(UpdateXRequest request) throws Exception;
}
The class I want to test:
#Service(ClassA.class)
public class ClassA extends VService implements UpdateX {
#Reference
#Inject
private Interface interface;
#Inject
public ClassA(...) {...}
#Override
public UpdateXResponse process(UpdateXRequest request) throws Exception {
UpdateXResponse response = initResponse(context, request, new UpdateXResponse());
UpdateXInput input = request.getInput();
UpdateXOutput output = new UpdateXOutput();
response.setOutput(output);
try {
firstMethodCall(...);
} catch (Exception t) {
throwCorrectException(t, logger);
}
return response;
}
private void firstMethodCall(...) throws Exception {
TypeF typeF = callInterfaceMethod(...);
...
}
/**
* Orchestrates Interface service
*/
protected TypeF callInterfaceMethod(...) {
...
request.setInput(input);
request.setHeader(header);
InterfaceResponse response = interface.process(request); // LINE ERROR - In this step interface is NULL when the test get this
return response;
}
}
And finally my class test:
#RunWith(PowerMockRunner.class)
#PrepareForTest(value = {ClassA.class,Interface.class} )
public class WithPowerMockUnitTest{
#InjectMocks
private ClassA classA;
private Interface interface;
#Before
public void setUp() throws Exception {
InterfaceRequest InterfaceRequest = createInterfaceRequest();
InterfaceResponse serviceUnavailableResponse = createInterfaceResponse();
Interface = Mockito.mock(Interface.class);
when(Interface.process(Mockito.any(InterfaceRequest.class))).thenReturn(serviceUnavailableResponse);
}
#Test
public void testh() throws SOAException {
InterfaceResponse res = interface.process(Mockito.any(InterfaceRequest.class)); // There all run ok. The interface is not null and return what i expected.
System.out.println("RES "+res);
}
#Test
public void test() {
assertNotNull(classA); // not null
assertNotNull(interface); // not null
}
#Test
public void newTest() throws Exception {
InterfaceRequest InterfaceRequest = createInterfaceRequest();
InterfaceResponse serviceUnavailableResponse = createInterfaceResponse();
UpdateXResponse response = ClassA.process(updateXRequest()); // PROBLEM!! When that get the LINE ERROR the interface is null! WHY?
}
}
I put some comments in the lines where the problem exists for me.
public interface A{
Response process(Request r) throws Exception;
}
public class B{
private Class_That_Override_Interface_method ctoim;
public Response function(){
X res = method_B();
}
protected X method_B(){
response res = ctoim.process(request); // That ctoim is always NULL when the test get that line/call
}
}
Thanks

Answer 1

You're missing the #Mock annotation on your Interface variable.
Therefore the mock is not injected into your classA and the newTest() fails. (In this case remove Interface = Mockito.mock(Interface.class); from the setUp method).
Alternativly remove the #InjectMocks annotation and create your class under test manually passing your mock into the constructor.
For this specific case (assuming its a different case from the last question)
there doesn't seem to be a need to involve PowerMockito. So unless you left out some relevant parts you might as well just use the MockitoJUnitRunner.
Ps.:
Also remeber what I said last time about compilable examples?
interface is a keyword and can't be used for variables.
You should also aim to write variables identical all the times (not Interface and interface / classA and ClassA)
And in case you haven't read it yet check out the help section about minmal reproducible examples.
Edit:
I fogot to mention that the line interface.process(Mockito.any(InterfaceRequest.class)); in testh() is actually invalid syntax. You should use ArgumentMatchers only for parameters of mocked methods.
Also consider adding the MockitoAnnotations.initMocks(this); to your setUp method, when using the PowerMockRunner.