powermock框架（建议不用,mockito已经支持mock静态方法 ）

一、为什么要用powermock？

• 能对private/static/final等方法mock
• 能mock方法中 ”new出来“的对象“

二、powermock的使用

1、 maven依赖

<dependency>
    <groupId>org.powermockgroupId>
    <artifactId>powermock-module-junit4artifactId>
    <version>2.0.0version>
    <scope>testscope>
dependency>

<dependency>
    <groupId>org.powermockgroupId>
    <artifactId>powermock-api-mockito2artifactId>
    <version>2.0.0version>
    <scope>testscope>
dependency>

2、springboot基础配置（测试基类）

@PreparwForeTest({被mock的静态方法})
@RunWith(PowerMockRunner.class)
@PowerMockRunnerDelegate(SpringJUnit4ClassRunner.class)
@PowerMockIgnore({"javax.net.ssl.*", "javax.management.*", "javax.crypto.*"})
@SpringBootTest
public class BasePowerMock {}

3、mock对象

1）@Mock和@MockBean

• @Mock（需要MockAnotation.init(this)初始化: 完全mock一个对象
  等于Mockito.mock(Object.class)
• @MockBean：mock对象替换Spring容器中的同样类型的bean

2）@Spy和@SpyBean

• @Spy： 不mock，则与普通对象一样
• @SpyBean: 不mock，则与Spring中的bean一样

4、stub

1)mock目标对象的public、private、final、static方法：

目标对象

public class MyThread {

    public void doMain(){
        System.out.println(doPublic());
        System.out.println(doPrivate());
        System.out.println(doFinal());
        System.out.println(doStatic());
    }

    public String doPublic(){
        return "this is real public";
    }

    public static String doStatic(){
        return "this is real private";
    }

    private String doPrivate(){
        return "this is real private";
    }

    public final String doFinal(){
        return "this is real final";
    }
    
}

mock方法

@RunWith(PowerMockRunner.class)
@PrepareForTest({MyThread.class,Thread.class})
public class MyThreadTest {

    @Test
    public void testMock() throws Exception {
        MyThread  myThread = PowerMockito.spy(new MyThread());

        PowerMockito.doReturn("this is mock public")
                .when(myThread,"doPublic");
        PowerMockito.doReturn("this is mock private")
                .when(myThread,"doPrivate");
        PowerMockito.doReturn("this is mock final")
                .when(myThread,"doFinal");
        //mock 静态方法
        PowerMockito.mockStatic(MyThread.class);
        PowerMockito.doReturn("this is mock static")
                .when(MyThread.class,"doStatic");

        myThread.doMain();
    }
}

结果：

注意点：

• mock静态方法，mock的是目标.class

2) mock目标对象中的方法中”new出来的对象“：

目标类

public class MockOutClass {
    public void doMain(){
        MyThread myThread = new MyThread();
        myThread.doMain();
    }
}

mock类

@RunWith(PowerMockRunner.class)
@PrepareForTest({MockOutClass.class,MyThread.class})
public class MockOutClassTest {
    @Test
    public void testMock() throws Exception {
        MockOutClass mockOutClass = PowerMockito.spy(new MockOutClass());
        //mock new
        MyThread myThread = PowerMockito.spy(new MyThread());
        PowerMockito.whenNew(MyThread.class).withAnyArguments().thenReturn(myThread);
        //mock method
        PowerMockito.doReturn("this is mockOut public")
                        .when(myThread).doPublic();
        PowerMockito.doReturn("this is mock private")
                .when(myThread,"doPrivate");
        PowerMockito.doReturn("this is mock final")
                .when(myThread,"doFinal");
        //mock 静态方法
        PowerMockito.mockStatic(MyThread.class);
        PowerMockito.doReturn("this is mock static")
                .when(MyThread.class,"doStatic");

        mockOutClass.doMain();
    }

}

4、verify

1) 方法调用次数

 - 默认一次   Mockito.verify(uploadDataToUmpService).uploadTotalCount(Mockito.anyList());
 - 自定义次数：
 			Mockito.verify(uploadDataToUmpService，Mockito》times（2）).uploadTotalCount(Mockito.anyList());

2）断言异常

断言异常

三、powermock原理探究

1.简单原理

PowerMock简单实现原理

• 当某个测试方法被注解@PrepareForTest标注以后，在运行测试用例时，会创建一个新org.powermock.core.classloader.MockClassLoader实例，然后加载该测试用例使用到的类（系统类除外）。
• PowerMock会根据你的mock要求，去修改写在注解@PrepareForTest里的class文件（当前测试类会自动加入注解中），以满足特殊的mock需求。例如：去除final方法的final标识，在静态方法的最前面加入自己的虚拟实现等。
• 如果需要mock的是系统类的final方法和静态方法，PowerMock不会直接修改系统类的class文件，而是修改调用系统类的class文件，以满足mock需求