template 
int mock(Origin old_func, Mock new_func, void *obj = nullptr);

void reset();

int global(int a, int b) {
    return a + b;
}

int fake_global(int a, int b) {
    //校验参数正确性，确定被测代码传入了正确的值
    assert(a == 3);
    assert(b == 2);
    //给一个返回值，配合被测代码走特定分支
    return a - b;
}

assert(global(3, 2) == 5);

//通过mock调用，完成函数动态替换
assert(0 == mock(&global, &fake_global));

//调用mock后的函数，可以看到返回值变了
assert(global(3, 2) == 1);

//结束mock
reset();

//函数行为恢复
assert(global(3, 2) == 5);

class A {
public:
    int member(int a) {return ++a;}
    static int static_member(int a) {return 200;}
    virtual int virtual_member() {return 400;}
};

int fake_member(A *pTihs, int a) {
		//由于是对成员函数插桩,这里需要这个this指针参数
    return --a;
}

A a;
assert(a.member(100) == 101);

mock(&A::member, fake_member);
assert(a.member(100) == 99);

reset();

assert(a.member(100) == 101);

int fake_static_member() {
	 //静态函数不需要this指针
    return 300;
}

assert(A::static_member(200) == 200);

mock(&A::static_member, fake_static_member);
assert(A::static_member(100) == 300);

reset();

assert(A::static_member(200) == 200);

int fake_virtual_member(A *pThis) {
    //虚函数同普通的成员函数由于,同样需要this指针
    return 500;
}

A a;
assert(a.virtual_member() == 400);

//虚函数mock需要多传一个相关类的对象，任意一个对象即可，跟实际代码中的对象没有关系
A a_obj;
mock(&A::virtual_member, fake_virtual_member, &a_obj);
assert(a.virtual_member() == 500);

reset();
assert(a.virtual_member() == 400);

int fake_write(int, char*, int) {
    return 100;
}

//直接写入一个无效的文件描述符，会失败
assert(write(5, "hello", 5) == -1);

//来一个假的wirte
mock(write, fake_write);
//模拟调用成功
assert(write(5, "hello", 5) == 100);

reset();

assert(write(5, "hello", 5) == -1);

printf '\x07' | dd of= bs=1 seek=160 count=1 conv=notrunc