powermock series 2 - 测试私有方法，私有构造函数

Getting Started

use : rely on EasyMock or Mockito and a test framework

Bypass Encapsulation mock 绕过封装

翻译自
https://github.com/powermock/powermock/wiki/Bypass-Encapsulation

Quick summary

Whitebox

class provides a set of methods which could you help bypass encapsulation if it required. Usually, it's not a good idea to get/modify non-public fields, but sometimes it's only way to cover code by test for future refactoring.

1. Use Whitebox.setInternalState(..) to set a non-public member of an instance or class. 设置内部私有成员
2. Use Whitebox.getInternalState(..) to get a non-public member of an instance or class. 获取内部私有成员
3. Use Whitebox.invokeMethod(..) to invoke a non-public method of an instance or class. 调用私有方法
4. Use Whitebox.invokeConstructor(..) to create an instance of a class with a private constructor. 调用私有构造函数

举例

• 1 调用私有方法

private int sum(int a, int b) {
    return a+b;
}

int sum = Whitebox. invokeMethod(myInstance, "sum", 1, 2);

• 2 私有方法重载情况

...
private int myMethod(int id) {      
    return 2*id;
}

private int myMethod(Integer id) {      
        return 3*id;
}
...

根据传入参数class判断用哪个

int result = Whitebox. invokeMethod(myInstance, new Class[]{int.class}, "myMethod", 1);

• 3 调用私有构造器

public class PrivateConstructorInstantiationDemo {

    private final int state;

    private PrivateConstructorInstantiationDemo(int state) {
        this.state = state;
    }

    public int getState() {
        return state;
    }
}

调用：

PrivateConstructorInstantiationDemo instance =  WhiteBox.invokeConstructor(
                PrivateConstructorInstantiationDemo.class, 43);

• 4. 构造器重载的情况

public class PrivateConstructorInstantiationDemo {

    private final int state;

    private PrivateConstructorInstantiationDemo(int state) {
        this.state = state;
    }

    private PrivateConstructorInstantiationDemo(Integer state) {
              this.state = state;
              // do something else
    }

    public int getState() {
        return state;
    }
}

调用：

PrivateConstructorInstantiationDemo instance = Whitebox.invokeConstructor(PrivateConstructorInstantiationDemo.class, new Class[]{Integer.class}, 43);