在Java程序的单元测试中常用的mock工具有Mockito和EasyMock。但是这两种mock工具都无法实现对静态、final、私有方法或类的mock。因此有了功能强大的PowerMock工具。PowerMock并不是一个独立、全新的工具而是在Mockito和EasyMock的基础上进行的扩展，它分别有针对Mockito级EasyMock的扩展实现。本文主要介绍PowerMock的常见用法：

1.pom依赖

<dependency>
    <groupId>junit</groupId>
    <artifactId>junit</artifactId>
        <version>4.10<version>
    <scope>test</scope>
</dependency>        
<dependency>
        <groupId>org.powermock</groupId>
        <artifactId>powermock-module-junit4</artifactId>
        <version>1.6.3</version>
        <scope>test</scope>
</dependency>    
<dependency>    
        <groupId>org.powermock</groupId>    
        <artifactId>powermock-api-mockito</artifactId>    
        <version>1.6.3</version>    
        <scope>test</scope>    
</dependency>

2.基本用法

2.1 测试类加上必要的注解

@RunWith(PowerMockRunner.class)
@PrepareForTest({ExtensionLoader.class,Configs.class})  //静态类，测试类本身（需要mock构造方法时）
@PowerMockIgnore("javax.management.*")

2.2 mock基本对象

测试 convert.convertAndHanlder(method,ref,bead)方法

@Mock
Convert convert;


when(convert.convertAndHanlder(eq(method),eq(ref),eq(bead))).thenReturn(bead);

2.3 mock无返回值的方法

@Mock
ProviderComposeConfig providerComposeConfig;


doNothing().when(providerComposeConfig).putSync(eq(providerConfig));

 2.4 mock方法执行异常场景

@Mock
ProviderComposeConfig providerComposeConfig;

doThrow(new Exception("执行失败")).when(providerComposeConfig).putSync(eq(providerConfig));

2.5 mock 静态方法

 测试Configs.getConfig（ProviderComposeConfig.class）方法

前提：@PrepareForTest注解中添加该类：ProviderComposeConfig.class

@Mock
ProviderComposeConfig configs;


PowerMockito.mockStatic(Configs.class);
when(Configs.getConfig(eq(ProviderComposeConfig.class))).thenReturn(configs);

mock无返回值的static方法

// "xxxUtil" 是类名 // "xxxStaticMethod" 是 static 方法的方法名 // 这里假设 "xxxStaticMethod" 需要两个参数，一个是 int 型，一个是 String 型 PowerMockito.doNothing().when(xxxUtil.class, "xxxStaticMethod", 1，"mysql");

mock可变参数传递

public class Demo {
    public static void test(String... args) {
        System.out.println(args);
    }
}

 测试方法：

@RunWith(PowerMockRunner.class)
@PrepareForTest({Demo.class})
@PowerMockIgnore("javax.management.*")
public class DemoTest {
    
    @Test
    public void test() throws Exception {
        PowerMockito.mockStatic(Demo.class);
        PowerMockito.doNothing().when(Demo.class,"test",eq("liu1"),eq("liu2"));
        Demo.test("liu1","liu2");
    }
    
}

 2.6 mock 构造方法

前提：@PrepareForTest注解中添加该类：HookContext.class

@Mock
HookContext context; 
 

//无参构造
PowerMockito.whenNew(HookContext.class).withNoArguments().thenReturn(context);

//有参构造
PowerMockito.whenNew(HookContext.class).withArguments(anystring()).thenReturn(context);

 ③完成实例

被测试类：

public class HandlerHook {

    public final static String id = "handler";

    @Override
    public Bead doCall(HookContext context, Bead bead, AccessId id) throws Throwable {
        ProviderComposeConfig configs = Configs.getConfig(ProviderComposeConfig.class);
        ProviderConfig config = configs == null ? null : configs.get(id);

        if (config == null) {
            // 即没有该服务，1.本地调用 2.客户端信息有误，访问IP:PORT 却没有服务
            return null;
        }

        // 拿到转换器，调用
        Convert convert = ExtensionLoader.getExtensionLoader(Convert.class).getExtensionById(ConvertProcessor.id);
        return convert.convertAndHanlder(config.getMethod(), config.getRef(), bead);
    }

}

 测试类：

@RunWith(PowerMockRunner.class)
@PrepareForTest({ExtensionLoader.class,Configs.class})
@PowerMockIgnore("javax.management.*")
public class HandlerHookTest {

    @Mock
    HookContext hookContext;
    
    @Mock
    Bead bead;
    
    @Mock
    AccessId accessId;
    
    @Mock
    ExtensionLoader<Convert> extensionLoader;
    
    @Mock
    ProviderComposeConfig configs;
    
    @Mock
    ProviderConfig config;
    
    @Mock
    Method method ;
    
    @Mock
    Object ref;
    
    @Mock
    Convert convert;
    
    private HandlerHook handlerHook = new HandlerHook();
    
    @Test
    public void doCall() throws Throwable {
        PowerMockito.mockStatic(Configs.class);
        when(Configs.getConfig(eq(ProviderComposeConfig.class))).thenReturn(configs);
        when(configs.get(eq(accessId))).thenReturn(config);
        
        PowerMockito.mockStatic(ExtensionLoader.class);
        when(ExtensionLoader.getExtensionLoader(eq(Convert.class))).thenReturn(extensionLoader);
        when(extensionLoader.getExtensionById(eq("map"))).thenReturn(convert);
        when(config.getMethod()).thenReturn(method);
        when(config.getRef()).thenReturn(ref);
        
        when(convert.convertAndHanlder(eq(method),eq(ref),eq(bead))).thenReturn(bead);
        assertEquals(bead, handlerHook.doCall(hookContext, bead, accessId));
    }
    
}