Mockito with void method in JUnit

Question

I have implemented a simple spring boot crud application to write test cases. I have faced a bit of trouble with the delete operation. When I use Mockito.when method then it is expected a return value and my delete method is non-return type.

Service Class

@Service
public class EmployeeServiceImpl  implements EmployeeService {

    private EmployeeDAO employeeDAO;

    @Autowired
    public EmployeeServiceImpl(EmployeeDAO employeeDAO)
    {
        this.employeeDAO=employeeDAO;
    }

    @Override
    public void deleteEmployee(Employee emp) throws IllegalArgumentException{
             employeeDAO.delete(emp);
    }

}

ServiceTest class

@ExtendWith(SpringExtension.class)
@SpringBootTest
public class EmployeeServiceImplTest {

    @MockBean
    private EmployeeDAO employeeDAO;

    @Autowired
    private EmployeeService employeeService;

@Test
public void testDeleteEmployee()
{
    int empId=1054;
    Employee employee=employee_2();
    employee.setEmpId(empId);

   // how to write test case for void method
}

private Employee employee_2()
    {
        Employee employee=new Employee();
        employee.setEmpName("NafazBenzema");
        employee.setSalary(12000.00);

        return employee;
    }

}

Answer 1

You can either use doNothing or doThrow on your mock to mock the behaviour of your mock.

Mockito.doNothing().when(employeeDAO).delete(any());

or

Mockito.doThrow(new RuntimeException()).when(employeeDAO).delete(any());

However, doNothing is not actually needed as this would be the default behaviour for a mock function with a void return type. You may want however to verify that this method was called. For example:

verify(employeeDAO).delete(any());

Answer 2

You can use Mockito.doNothing():

Mockito.doNothing().when(employeeDAO).deleteEmployee(Mockito.any());