問題描述

假設我有這樣的課程:

public class MyClass {

    Dao dao;

    public String myMethod(Dao d) {

        dao = d;

        String result = dao.query();

        return result;
    } 
}

我想用 mockito 測試它.所以我創建了一個模擬對象并以這種方式調用該方法進行測試:

I want to test it with mockito. So I create a mock object and I call the method to test in that way:

Dao mock = Mockito.mock(Dao.class);

Mockito.when(mock.myMethod()).thenReturn("ok");

new MyClass().myMethod(mock);

但是，假設我有一個這樣的課程:

But, suppose instead I have a class like that:

public class MyClass {

    Dao dao = new Dao();

    public String myMethod() {

        String result = dao.query();

        return result;
    } 
}

現在我無法將我的模擬作為參數傳遞，那么我將如何測試我的方法?有人可以舉個例子嗎?

Now I cannot pass my mock as an argument, so how I gonna test my method? Can someone show an example?

推薦答案

從根本上說，您試圖用替代實現替換私有字段，這意味著您違反了封裝.您唯一的其他選擇是重組類或方法，使其更適合測試.

Fundamentally, you're trying to replace a private field with an alternative implementation, which means you'd violate encapsulation. Your only other option is to restructure the class or method, to make it better-designed for testing.

評論中有很多簡短的答案，所以我在這里將它們匯總(并添加我自己的幾個)作為社區 Wiki.如果您有任何替代方案，請隨時在此處添加.

There are a lot of short answers in the comments, so I'm aggregating them here (and adding a couple of my own) as Community Wiki. If you have any alternatives, please feel free to add them here.

• 為相關字段創建一個 setter，或放寬該字段的可見性.

• Create a setter for the field in question, or relax the field's visibility.

創建一個采用 DAO 的依賴注入覆蓋或靜態方法，并將公共實例方法委托給它.改為測試更靈活的方法.

Create a dependency-injecting override or static method that takes a DAO, and make the public instance method delegate to it. Test the more-flexible method instead.

public String myMethod() { return myMethod(dao); }
String myMethod(Dao dao) { /* real implementation here */ }