我依赖于可能响应也可能不响应的硬件。因此,我经常在编写函数时超时。系统时间是脆性单元测试的已知来源,因此注入受控和稳定的时间似乎是测试的好主意。
我想知道std::chrono中是否有任何设施可以帮助实现这一点。我看到的另一种选择是围绕系统时间编写一个包装器,并依赖于该适配器。
下面是一个包装器外观的最小示例。
#pragma once
#include <memory>
#include <chrono>
#include <thread>
#include <iostream>
using std::chrono::system_clock;
using std::chrono::milliseconds;
using std::shared_ptr;
using std::make_shared;
class Wrapped_Clock
{
public:
virtual system_clock::time_point Now() { return system_clock::now(); }
virtual void Sleep(milliseconds ms) { std::this_thread::sleep_for(ms); }
};
class Mock_Clock : public Wrapped_Clock
{
private:
system_clock::time_point now;
public:
Mock_Clock() : now(system_clock::now()){}
~Mock_Clock() {}
system_clock::time_point Now() { return now; }
void Sleep(milliseconds ms) { }
};
class CanTimeOut
{
private:
shared_ptr<Wrapped_Clock> sclock;
public:
CanTimeOut(shared_ptr<Wrapped_Clock> sclock = make_shared<Wrapped_Clock>()) : sclock(sclock) {}
~CanTimeOut() {}
milliseconds TimeoutAction(milliseconds maxtime)
{
using std::chrono::duration_cast;
int x = 0;
system_clock::time_point start = sclock->Now();
system_clock::time_point timeout = sclock->Now() + maxtime;
while (timeout > sclock->Now() && x != 2000)
{
sclock->Sleep(milliseconds(1));
++x;
}
milliseconds elapsed = duration_cast<milliseconds>(sclock->Now() - start);
return elapsed;
}
};
#define EXPECT_GE(left, right, test)
{ if (!(left >= right)) {
std::cout << #test << " " << "!(" << left << " >= " << right << ")" << std::endl;
} }
#define EXPECT_EQ(expected, actual, test)
{ if (!(expected == actual)) {
std::cout << #test << " " << "!(" << expected << " == " << actual << ")" << std::endl;
} }
void TestWithSystemClock()
{
CanTimeOut cto;
long long timeout = 1000;
milliseconds actual = cto.TimeoutAction(milliseconds(timeout));
EXPECT_GE(actual.count(), timeout, TestWithSystemClock);
}
void TestWithMockClock()
{
CanTimeOut cto(make_shared<Mock_Clock>());
milliseconds actual = cto.TimeoutAction(milliseconds(1000));
EXPECT_EQ(0, actual.count(), TestWithMockClock);
}
int main()
{
TestWithSystemClock();
TestWithMockClock();
}
其中有多少可以用std::chrone的功能来替换?
编辑1:
- "你到底在测试什么"我将时间作为一个测试条件来控制,以改变依赖于时间的方法调用的行为。测试表明,模拟时间和控制行为作为一个概念是有效的,并表明了我对它的理解。最小示例的目的是表明我对模拟时间的理解,以便更容易地向
std::
设施显示差异 - "花大约10个字来说明测试应该对比什么"一次测试总是超时。另一项测试显示没有时间流逝。不包括控制精确且非零时间流逝的第三次测试
- "此外,睡眠与时钟无关。这不是计时功能"我需要它来确保一个测试在超时之前永远不会循环超过一定量,这模拟了一些需要时间和可能超时的操作。另一方面,我想建立一个快捷方式,这样第二次测试就不会浪费时间等待。也可以不模拟睡眠,但测试需要2秒。我认识到睡眠不是一个时间特征,因此具有误导性
相反,它看起来是在嘲笑std::this_thread::sleep
。
这有点棘手,因为它是一个只有自由函数的命名空间。很难为测试目的"注入"命名空间。因此,实际上,您应该用自己的类型包装该名称空间中的函数。
我会使用静态依赖注入,就像C++:
在Coliru上直播
#include <memory>
#include <chrono>
#include <thread>
#include <iostream>
using std::chrono::system_clock;
using std::chrono::milliseconds;
struct production {
using clock = std::chrono::system_clock;
struct this_thread {
template<typename... A> static auto sleep_for(A&&... a) { return std::this_thread::sleep_for(std::forward<A>(a)...); }
template<typename... A> static auto sleep_until(A&&... a) { return std::this_thread::sleep_until(std::forward<A>(a)...); }
};
};
struct mock {
struct clock : std::chrono::system_clock {
using base_type = std::chrono::system_clock;
static time_point now() { static auto onetime = base_type::now(); return onetime; }
};
struct this_thread {
template<typename... A> static auto sleep_for(A&&... a) {}
template<typename... A> static auto sleep_until(A&&... a) {}
};
};
template <typename services = production,
typename clock = typename services::clock,
typename this_thread = typename services::this_thread>
class CanTimeOut
{
public:
milliseconds TimeoutAction(milliseconds maxtime)
{
using std::chrono::duration_cast;
int x = 0;
auto start = clock::now();
auto timeout = clock::now() + maxtime;
while (timeout > clock::now() && x != 2000)
{
this_thread::sleep_for(milliseconds(1));
++x;
}
milliseconds elapsed = duration_cast<milliseconds>(clock::now() - start);
return elapsed;
}
};
#define EXPECT_GE(left, right, test)
{ if (!(left >= right)) {
std::cout << #test << " " << "!(" << left << " >= " << right << ")" << std::endl;
} }
#define EXPECT_EQ(expected, actual, test)
{ if (!(expected == actual)) {
std::cout << #test << " " << "!(" << expected << " == " << actual << ")" << std::endl;
} }
void TestWithSystemClock()
{
CanTimeOut<> cto;
long long timeout = 1000;
milliseconds actual = cto.TimeoutAction(milliseconds(timeout));
EXPECT_GE(actual.count(), timeout, TestWithSystemClock);
}
void TestWithMockClock()
{
CanTimeOut<mock> cto;
milliseconds actual = cto.TimeoutAction(milliseconds(1000));
EXPECT_EQ(0, actual.count(), TestWithMockClock);
}
int main()
{
TestWithSystemClock();
TestWithMockClock();
}
处理此问题的另一种方法是定义模拟时钟并指定要用作模板参数的时钟类型。
#include <chrono>
#include <iostream>
#include <thread>
#include "sim_clock.hpp"
using namespace std::chrono;
template <typename clock_t> void Sleep(milliseconds ms)
{
std::this_thread::sleep_for(ms);
}
template <> void Sleep<sim_clock>(milliseconds ms)
{
sim_clock::increment_by(ms);
}
template <typename clock_t = std::chrono::steady_clock> class CanTimeOut
{
public:
CanTimeOut() = default;
~CanTimeOut() = default;
milliseconds TimeoutAction(milliseconds maxtime)
{
int x = 0;
auto start = clock_t::now();
auto timeout = start + maxtime;
while(timeout > clock_t::now()) { Sleep<clock_t>(milliseconds(1)); }
return duration_cast<milliseconds>(clock_t::now() - start);
}
};
#define EXPECT_GE(left, right, test)
{
if(!(left >= right)) {
std::cout << #test << " "
<< "!(" << left << " >= " << right << ")" << std::endl;
}
}
void TestWithSystemClock()
{
CanTimeOut<> cto;
long long timeout = 1000;
milliseconds actual = cto.TimeoutAction(milliseconds(timeout));
EXPECT_GE(actual.count(), timeout, TestWithSystemClock);
}
void TestWithMockClock()
{
CanTimeOut<sim_clock> cto;
long long timeout = 1000;
milliseconds actual = cto.TimeoutAction(milliseconds(timeout));
sim_clock::increment_by(milliseconds(timeout));
EXPECT_GE(actual.count(), timeout, TestWithSystemClock);
}
int main()
{
TestWithSystemClock();
TestWithMockClock();
}
以下是基于steady_clock
:的模拟时钟定义
#pragma once
#include <chrono>
struct sim_clock {
typedef std::chrono::steady_clock::rep rep;
typedef std::chrono::steady_clock::period period;
typedef std::chrono::steady_clock::duration duration;
typedef std::chrono::steady_clock::time_point time_point;
static time_point now() noexcept;
static void increment_by(sim_clock::duration d) noexcept;
static constexpr bool is_steady = true;
static time_point _now;
};
和实施:
#include "sim_clock.hpp"
sim_clock::time_point sim_clock::_now;
sim_clock::time_point sim_clock::now() noexcept
{
return _now;
}
void sim_clock::increment_by(sim_clock::duration d) noexcept
{
_now += d;
}