Powermockito私有方法模拟NullPointerExcture。调用私有方法

Question

我试图模拟一个私有方法（executeGetRequest），在我声明要为私有方法返回的模拟的那一行中，私有方法实际上是用null参数执行的，因此抛出了一个NullPointerException。

VlcPlayerMinimal。爪哇：

package com.nicobrest.kamehouse.vlcrc.model;

public class VlcPlayerMinimal {

  public static void main(String[] args) {
    String vlcRcStatus = new VlcPlayerMinimal().getVlcRcStatus();
    System.out.println(vlcRcStatus);
  }

  public String getVlcRcStatus() {
    Client client = new Client();
    GetRequest getRequest = new GetRequest();
    String vlcRcStatus = executeGetRequest(client, getRequest);
    return vlcRcStatus;
  }

  private String executeGetRequest(Client client, GetRequest getRequest) {
    return client.execute(getRequest);
  }

  private class Client {
    public String execute(GetRequest getRequest) {
      return "{status: playing, id: 1}";
    }
  }
  private class GetRequest { 
  }
}

VlcPlayerMinimalTest。爪哇：

package com.nicobrest.kamehouse.model;

import static org.junit.Assert.*;
import static org.mockito.ArgumentMatchers.any;

import com.nicobrest.kamehouse.vlcrc.model.VlcPlayerMinimal;

import org.junit.Test;
import org.powermock.api.mockito.PowerMockito;

public class VlcPlayerMinimalTest {

  @Test
  public void getVlcRcStatusTest() {
    VlcPlayerMinimal vlcPlayerSpy = PowerMockito.spy(new VlcPlayerMinimal());
    try {
      PowerMockito.doReturn("{status: stopped, id: 2}").when(vlcPlayerSpy, "executeGetRequest", any(), any());
      String vlcRcStatus = vlcPlayerSpy.getVlcRcStatus();
      System.out.println(vlcRcStatus);
    } catch (Exception e) {
      e.printStackTrace();
      fail("Unexpected exception thrown.");
    }
  }
}

堆栈跟踪：

java.lang.NullPointerException
    at com.nicobrest.kamehouse.vlcrc.model.VlcPlayerMinimal.executeGetRequest(VlcPlayerMinimal.java:18)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
    at java.lang.reflect.Method.invoke(Unknown Source)
    at org.powermock.reflect.internal.WhiteboxImpl.performMethodInvocation(WhiteboxImpl.java:1846)
    at org.powermock.reflect.internal.WhiteboxImpl.doInvokeMethod(WhiteboxImpl.java:810)
    at org.powermock.reflect.internal.WhiteboxImpl.invokeMethod(WhiteboxImpl.java:675)
    at org.powermock.reflect.Whitebox.invokeMethod(Whitebox.java:401)
    at org.powermock.api.mockito.internal.expectation.PowerMockitoStubberImpl.when(PowerMockitoStubberImpl.java:95)
    at com.nicobrest.kamehouse.model.VlcPlayerMinimalTest.getVlcRcStatusTest(VlcPlayerMinimalTest.java:17)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
...

它似乎PowerMockito实际上是调用的方法，我试图在行PowerMockito.do返回（{状态：停止，id： 2}）。

它抛出异常，因为客户端是null，所以它在null上调用执行（getClient），但这是我在测试中试图避免调用的方法。

有没有办法解决这个问题？我尝试了一段时间，但没有成功。

我正在使用Java8、powermock 1.7.3和JUnit4.12

Answer 1

此测试成功：

package foo.bar;

import static org.junit.Assert.*;

import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.Mockito;
import org.powermock.api.mockito.PowerMockito;
import org.powermock.core.classloader.annotations.PrepareForTest;
import org.powermock.modules.junit4.PowerMockRunner;

@RunWith(PowerMockRunner.class)
@PrepareForTest(VlcPlayerMinimal.class)
public class VlcPlayerMinimalTest {

  @Test
  public void getVlcRcStatusTest() {
    VlcPlayerMinimal vlcPlayerSpy = PowerMockito.spy(new VlcPlayerMinimal());
    try {
      PowerMockito.doReturn("{status: stopped, id: 2}").when(vlcPlayerSpy, "executeGetRequest", Mockito.any(), Mockito.any());
      String vlcRcStatus = vlcPlayerSpy.getVlcRcStatus();
      System.out.println(vlcRcStatus);
    } catch (Exception e) {
      e.printStackTrace();
      fail("Unexpected exception thrown.");
    }
  }
}

您需要这些类级注释：

@RunWith(PowerMockRunner.class)
@PrepareForTest(VlcPlayerMinimal.class)

控制台输出：

{状态：已停止，id:2}