### Question:
AuthenticationServiceImpl implements AuthenticationService { public User getAuthenticatedUser() { return contextService.getAuthenticatedUser(); } AuthenticationServiceImpl(ContextService contextService); User getAuthenticatedUser();  }### Answer:
@Test public void shouldDelegateCallToContextService(){ AuthenticationServiceImpl service = new AuthenticationServiceImpl(contextService); User user = new User(); when(contextService.getAuthenticatedUser()).thenReturn(user); User authenticatedUser = service.getAuthenticatedUser(); verify(contextService).getAuthenticatedUser(); assertSame(user,authenticatedUser); }