title: Mockito Inject mock into Spy object
body: <p>I'm writing a test case for a Class which has a 2 level of dependency injection. I use @Spy annotation for the 1 level dependency injection object, and I would like to Mock the 2nd level of injection. However, I kept getting null pointer exception on the 2nd level. Is there any way that I inject the mock into the @Spy object?</p>
  
  <pre><code>public class CarTestCase{
      @Mock
      private Configuration configuration;
  
      @Spy 
      private Engine engine;
  
      @InjectMocks 
      private Car car;
  
      @Test
      public void test(){
  
         Mockito.when(configuration.getProperties("")).return("Something");
         car.drive();
      }
  
  }
  
  public class Car{
      @Inject
      private Engine engine;
  
      public void drive(){
          engine.start();
      }
  }
  
  public class Engine{
      @Inject 
      private Configuration configuration;
  
      public void start(){
          configuration.getProperties();   // null pointer exception
      }
  
  }
  </code></pre>