java - 用于泛型类扩展的 Mockito/Powermock 类构造

Question

不确定我的问题措辞是否正确，但我正在尝试模拟作为泛型传递到我想要测试的对象中的类的构造。下面是我正在测试的对象中发生的情况的示例:

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

学习者是我想要模拟的，它是我构建的各种学习者类(class)的接口(interface)。我不想在这里测试他们的逻辑，这就是为什么我想 mock 他们并控制他们返回的内容。我正在尝试使用以下设置(静态学习器类没有构造函数参数):

@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 无法构造学习器，因为它说找不到构造函数。这是有道理的，因为 Learner 类只是一个接口(interface)。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 呢？

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 关键字时起作用，例如 new StaticLearner()。如果您使用StaticLearner.class.newInstance()，它将不起作用。

• 如果您想模拟 MyClass，请将 Learner 对象的创建委托(delegate)给新工厂类 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() {
          ...
      }
  }
  

• 现在模拟工厂类以返回模拟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();
       }
  
   }