Mockito/Powermock class 构造通用 class 扩展

Question

不确定我的问题措辞是否正确，但我正在尝试模拟 class 的构造，该 class 作为泛型传递到我要测试的对象中。下面是我正在测试的对象中发生的事情的示例：

MyClass(boolean historic, Class<? extends Learner> learner) {
    this.learner = learner.newInstance();
    this.historic = historic;
}

Learner 是我要模拟的，它是我构建的各种学习者 classes 的界面。我不想在这里测试他们的逻辑，这就是为什么我想嘲笑他们并控制他们 return。我正在尝试使用以下设置（静态学习器 class 没有构造函数参数）：

@Test
@PrepareForTest({MyClass.class, Learner.class, StaticLearner.class})
public void test() {
    Learner mockLearner = Mockito.mock(StaticLearner.class);          
    PowerMockito.whenNew(Learner.class)
            .withNoArguments()
            .thenReturn(mockLearner);

    MyClass myClass = new MyClass(true, StaticLearner.class);
    myClass.process();
}

问题是 Powermock 无法构造学习者，因为它说找不到构造函数。这是有道理的，因为 Learner class 只是一个接口。那么当 StaticLearner 只是从 Learner 继承的泛型时，我该如何模拟传入和构造的 StaticLearner？

这是我收到的错误：

org.powermock.reflect.exceptions.ConstructorNotFoundException: 
No constructor found in class 'com.myco.processing.learners.Learner' with parameter types: [ <none> ].

Answer 1

将 PowerMockito.whenNew(Learner.class) 替换为 PowerMockito.whenNew(StaticLearner.class)。例如，

    @Test
    @PrepareForTest({MyClass.class})
    public void test() throws Exception {
        StaticLearner mockLearner = Mockito.mock(StaticLearner.class);

        PowerMockito.whenNew(StaticLearner.class)
                .withNoArguments()
                .thenReturn(mockLearner);

        MyClass myClass = new MyClass(true, StaticLearner.class);
        myClass.process();
    }

更新

PowerMockito.whenNew 在使用 new 关键字时有效，例如 new StaticLearner()。如果您使用 StaticLearner.class.newInstance().

它将不起作用

如果要模拟MyClass，将Learner对象的创建委托给新工厂class，LearnerFactory.

public class LearnerFactory {

    public static Learner getInstance(
        Class<? extends Learner> learner) throws IllegalAccessException, InstantiationException {

        return learner.newInstance();
    }
}

public class MyClass {

    private boolean historic;

    private Learner learner;

    public MyClass(boolean historic,
        Class<? extends Learner> learner) throws IllegalAccessException, InstantiationException {
        this.learner = LearnerFactory.getInstance(learner);
        this.historic = historic;
    }

    public void process() {
        ...
    }
}

现在模拟工厂 class 到 return 模拟 StaticLearner.

 @RunWith(PowerMockRunner.class)
 @PrepareForTest({MyClass.class, LearnerFactory.class})
 public class MyClassTest {

     @Test
     public void test2() throws Exception {             
         StaticLearner mockLearner = 
             PowerMockito.mock(StaticLearner.class);
         //if needed
         when(mockLearner.doSomething(anyString()))
             .thenReturn("dummy");

         PowerMockito.mockStatic(LearnerFactory.class);
         when(LearnerFactory.getInstance(eq(StaticLearner.class)))
            .thenReturn(mockLearner);

         MyClass myClass = new MyClass(true, StaticLearner.class);
         myClass.process();
     }

 }

Answer 2

显然对 learner.newInstance() 的调用没有参数。即使有 id，它们也会作为参数传递给构造函数。

那么为什么不直接将 learner.newInstance() 的结果作为参数传递给这个构造函数呢？然后你可以传入一个 "regular" 模拟，你就不需要 ~~PowerMock~~.

Mockito/Powermock class 构造通用 class 扩展

Mockito/Powermock class construction for generic class extension

java

generics

unit-testing

mockito

powermockito

更新