如何使用 Mockito/Powermock 模拟枚举单例类? [英] How to mock an enum singleton class using Mockito/Powermock?

问题描述

我不确定如何模拟枚举单例类.

I am unsure on how to mock an enum singleton class.

public enum SingletonObject{
  INSTANCE;
  private int num;

  protected setNum(int num) {
    this.num = num;
  }

  public int getNum() {
    return num;
  }

我想在上面的例子中存根 getNum()，但我不知道如何模拟实际的 SingletonObject 类.我认为使用 Powermock 来准备测试会有所帮助，因为枚举本质上是最终的.

I'd like to stub getNum() in the above example, but I can't figure out how to mock the actual SingletonObject class. I thought using Powermock to prepare the test would help since enums are inherently final.

//... rest of test code
@Test
public void test() {
  PowerMockito.mock(SingletonObject.class);
  when(SingletonObject.INSTANCE.getNum()).thenReturn(1); //does not work
}

这是使用 PowerMockMockito 1.4.10 和 Mockito 1.8.5.

This is using PowerMockMockito 1.4.10 and Mockito 1.8.5.

推荐答案

如果你想找出 INSTANCE 返回的内容，你可以这样做，但它有点讨厌(使用反射和字节码操作).我创造了 &使用 PowerMock 1.4.12/Mockito 1.9.0 测试了一个包含三个类的简单项目.所有类都在同一个包中.

If you want to stub out what INSTANCE returns, you can do it but it's kind of nasty (using reflection & bytecode manipulation). I created & tested a simple project with three classes using the PowerMock 1.4.12 / Mockito 1.9.0. All classes were in the same package.

public enum SingletonObject {
    INSTANCE;
    private int num;

    protected void setNum(int num) {
        this.num = num;
    }

    public int getNum() {
        return num;
    }
}

SingletonConsumer.java

public class SingletonConsumer {
    public String consumeSingletonObject() {
        return String.valueOf(SingletonObject.INSTANCE.getNum());
    }
}

SingletonConsumerTest.java

import static org.junit.Assert.*;
import static org.powermock.api.mockito.PowerMockito.*;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;
import org.powermock.reflect.Whitebox;

@RunWith(PowerMockRunner.class)
@PrepareForTest({SingletonObject.class})
public class SingletonConsumerTest {
    @Test
    public void testConsumeSingletonObject() throws Exception {
        SingletonObject mockInstance = mock(SingletonObject.class);
        Whitebox.setInternalState(SingletonObject.class, "INSTANCE", mockInstance);

        when(mockInstance.getNum()).thenReturn(42);

        assertEquals("42", new SingletonConsumer().consumeSingletonObject());
    }
}

对 Whitebox.setInternalState 的调用将 INSTANCE 替换为您可以在测试中操作的模拟对象.

The call to the Whitebox.setInternalState replaces INSTANCE with a mock object that you can manipulate within your test.

这篇关于如何使用 Mockito/Powermock 模拟枚举单例类?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！