title: Mockito Exception - when() requires an argument which has to be a method call on a mock
body: <p>I have a very simple test case that is using Mockito and Spring Test framework. When I do </p>
  
  <pre><code>when(pcUserService.read("1")).thenReturn(pcUser);
  </code></pre>
  
  <p>I get this exception. </p>
  
  <pre><code>org.mockito.exceptions.misusing.MissingMethodInvocationException: 
  when() requires an argument which has to be 'a method call on a mock'.
  For example:
      when(mock.getArticles()).thenReturn(articles);
  
  Also, this error might show up because:
  1. you stub either of: final/private/equals()/hashCode() methods.
     Those methods *cannot* be stubbed/verified.
  2. inside when() you don't call method on mock but on some other object.
  
      at com.project.cleaner.controller.test.PcUserControllerTest.shouldGetPcUser(PcUserControllerTest.java:93)
      at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
      at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
      at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
      at java.lang.reflect.Method.invoke(Unknown Source)
      at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
  </code></pre>
  
  <p>I have tried with different methods but keep on getting this error message. I am using Spring 3.1.0.RELEASE with Mockito. Please share and guide me in the right direction.</p>