How to handle objects created within the method under test - spring

Question

I have the following model classes:
#Data
public class Address {
private String street;
private int number;
}
#Data
public class Person {
private String name;
private Address address;
}
and the following services:
#Service
public class MyService {
private final OtherService otherService;
public MyService(OtherService otherService) {
this.otherService = otherService;
}
public void create() {
Person myPerson = new Person();
myPerson.setName("John");
otherService.synchronize(myPerson);
myPerson.getAddress().setNumber(12);
}
}
#Service
public class OtherService {
public void synchronize(Person person) {
Address address = new Address();
address.setStreet("sample street");
address.setNumber(123);
person.setAddress(address);
}
}
I want to write a unit test for MyService. This is the not working version of the test:
#ExtendWith(SpringExtension.class)
class MyServiceTest {
#Mock OtherService otherService;
#InjectMocks MyService myService;
#Test
void test_create() {
// GIVEN
doNothing().when(otherService).synchronize(any(Person.class));
// WHEN
myService.create();
// THEN
verify(otherService).synchronize(any());
}
}
This fails because the myPerson object is created within the method being tested and therefore I get a NullPointerException when running the test. How could I deal with this issue? should I capture the value passed to the otherService?

Answer 1

There's a little complexity but it's not bad. Replace your doNothing call with something like this:
Mockito.doAnswer(
new Answer<Void>() {
public Void answer(InvocationOnMock invocation) throws Exception {
Person arg = invocation.getArgument(0);
arg.setAddress(new Address());
return;
}
}).when(otherService).synchronize(any(Person.class));