如何模拟提供用JMockit模拟的类实例的静态方法？

Question

我试图模拟一个单例类(SessionDataManager)，通过调用静态getInstance（）方法获得一个实例，但所有尝试似乎都返回null。

我试过了

    @Mocked SessionDataManager sessionDataManager;

        new MockUp<SessionDataManager>(){
            @Mock
            public SessionDataManager getInstance(Invocation invocation) {

                return invocation.getInvokedInstance(); 
            }
        };

Answer 1

我建议看一下文档，但这里有两个完整的示例测试：

public final class ExampleTest {
    public static final class SessionDataManager {
        private static final SessionDataManager instance = new SessionDataManager();
        public static SessionDataManager getInstance() { return instance; }
        public void doSomething() { throw new UnsupportedOperationException("to do"); }
    }

    @Test
    public void mockingASingleton(@Mocked SessionDataManager mockInstance) {
        SessionDataManager singletonInstance = SessionDataManager.getInstance();

        assertSame(mockInstance, singletonInstance);
        singletonInstance.doSomething(); // mocked, won't throw
    }

    @Test
    public void mockingASingletonWithAMockUp() {
        new MockUp<SessionDataManager>() {
            // no point in having a @Mock getInstance() here
            @Mock void doSomething() { /* whatever */ }
        };

        SessionDataManager singletonInstance = SessionDataManager.getInstance();
        singletonInstance.doSomething(); // redirects to the @Mock method, won't throw
    }
}