PowerMock常见用法

import 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({ MyClass.class})  
public class StaticClassSampleTest {  
  
	@Test  
	public void testPrivateMethod() throws Exception {  
		// 模拟 private的方法  
		MyClass spy = PowerMockito.spy(new MyClass());  
		PowerMockito.doReturn(3).when(spy, "private_method", 1);  
		Assert.assertEquals(3, spy.test_private_method(1));  
		PowerMockito.verifyPrivate(spy, Mockito.times(1)).invoke("private_method", 1);  
	}  
  
	@Test  
	public void testStaticReturnMethod() throws Exception {  
		// 模拟 静态有返回值的方法  
		PowerMockito.mockStatic(MyClass.class);  
		Mockito.when(MyClass.static_return_method()).thenReturn(2);  
		Assert.assertEquals(2, MyClass.static_return_method());  
	}  
  
	@Test  
	public void testVoidMethod() throws Exception {  
		// 模拟 不执行void的方法  
		MyClass spy = PowerMockito.spy(new MyClass());  
		PowerMockito.doNothing().when(spy).void_method();  
		spy.void_method();  
	}  
  
	@Test  
	public void testStaticMethod1() throws Exception {  
		// 模拟 不执行没参数的静态void的方法  
		PowerMockito.mockStatic(MyClass.class);  
		PowerMockito.doNothing().when(MyClass.class, "static_void_method");  
		MyClass.static_void_method();  
	}  
  
	@Test  
	public void testStaticMethod2() throws Exception {  
		// 模拟 不执行带参数的静态void的方法  
		PowerMockito.mockStatic(MyClass.class);  
		PowerMockito.doNothing().when(MyClass.class, "staticMethod", "123");  
		MyClass.staticMethod("123");  
  
		PowerMockito.doNothing().when(MyClass.class, "staticMethod", Mockito.anyString());  
		MyClass.staticMethod("456");  
	}  
  
}  
  
class MyClass {  
  
	final private int private_method(int a) {  
		return a;  
	}  
  
	public int test_private_method(int a) {  
		return private_method(a);  
	}  
  
	public static int static_return_method() {  
		return 1;  
	}  
  
	void void_method() {  
		throw new IllegalStateException("should not go here");  
	}  
  
	public static void static_void_method() {  
		throw new IllegalStateException("should not go here");  
	}  
  
	public static void staticMethod(String a) {  
		throw new IllegalStateException(a);  
	}  
}  

    maven依赖

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-all</artifactId>
    <version>1.8.5</version>
</dependency>
<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-module-junit4</artifactId>
    <version>1.4.10</version>
</dependency>
<dependency>
    <groupId>org.powermock</groupId>
    <artifactId>powermock-api-mockito</artifactId>
    <version>1.4.10</version>
</dependency> 

    另外补一下，测试目标方法内部对象的mock方式：

// 测试目标代码：
public class ClassUnderTest {
    public boolean callInternalInstance(String path) {
        File file = new File(path); 
        return file.exists(); 
    }
}
// 测试用例代码
@RunWith(PowerMockRunner.class) 
public class TestClassUnderTest{
    @Test 
    @PrepareForTest(ClassUnderTest.class) 
    public void testCallInternalInstance() throws Exception{
        File file = PowerMockito.mock(File.class); 
        ClassUnderTest underTest = new ClassUnderTest();
        PowerMockito.whenNew(File.class).withArguments("bbb").thenReturn(file);
        PowerMockito.when(file.exists()).thenReturn(true); 
        Assert.assertTrue(underTest.callInternalInstance("bbb")); 
    ｝
｝

 *当某个测试方法被注解@PrepareForTest标注以后，
 在运行测试用例时，会创建一个新的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。