code: public static <T> OngoingStubbing<T> when(Class<?> clazz, String methodToExpect, Object... arguments)
          throws Exception {
          return Mockito.when(Whitebox.<T>invokeMethod(clazz, methodToExpect, arguments));
      }
docs: Expect a static private or inner class method call.
  
  @throws Exception If something unexpected goes wrong.
  @see PowerMockito#when(Object)