title: Why @MockBean and @InjectMocks cause BeanCreationException?
body: <p>When I write spring boot test and define service as following:</p>
  
  <pre><code>@MockBean
  @InjectMocks
  private Service service;
  </code></pre>
  
  <p>i got <em>BeanCreationException: Could not inject field ... cannot have an existing value</em>
  Why ?</p>
  
  <p>Why i cannot have my service mocked and all its autowired fields mocked as well ?</p>