如何使用Mockito / Powermock模拟一个枚举单身班？ [英] How to mock an enum singleton class using Mockito/Powermock?

问题描述

我不确定如何模拟一个枚举单身人士类。

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放getNum（），但是我不能弄清楚如何模拟实际的SingletonObject类。我认为使用Powermock来准备测试将有助于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

如果你想扼杀INSTANCE返回的内容，你可以做到这一点，但这很糟糕（使用反射和放大;字节码操作）。我创造了&使用PowerMock 1.4.12 / Mockito 1.9.0测试了一个使用三个类的简单项目。所有课程都在同一个包中。

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

SingletonConsumer.java

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

SingletonConsumerTest.java

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());
    }
}

调用 Whitebox .setInternalState 用您可以在测试中操作的模拟对象替换 INSTANCE 。

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

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