JMockit MockUp ref: http://qiita.com/NewGyu/items/0380fa2a3d7f1d020512

file0.java

@Mocked
private Fuga fuga;
 :
 :
new Expectations(){{
   fuga.getName(); result="ホゲ男";
}}

file3.java

@Mocked
 private PageEntityService pageEntityService;
 :
 :
new Expectations(){{
   pageEntityService.createNewContent(); result=new Page();
}}

テストメソッド

@Test
public void test() {
    PageCreateAction pageCreator = new PageCreateAction();
    Deencapsulation.setField(pageCreator, pageEntityService);

    pageCreator.process(site);

    new Verifications() {{
        List<Page> pages;
        pageRepository.save(pages = withCapture());
        assertThat(pages.size(), is(0));
    }};
}

モックの宣言

 private PageEntityService pageEntityService = new PageEntityService();

 @BeforeClass
 public static void beforeClass() {
     new MockUp<PageEntityService>() {
        @Mock
        public Page createNewContent() {
            return new Page();
        }
    };
 }