c++ - 如何实例化 std::exception_ptr 以进行单元测试

Question

我有一个运行异步网络工作线程的系统，并定期检查该工作线程是否存储了一些std::exception_ptr。在这种情况下，它可能会抛出错误，或以其他方式报告错误。简单的例子:

#include <exception>
#include <gmock/gmock.h>

// simplified Network interface and the mock
struct INetwork {
    virtual std::exception_ptr getExceptionPtr() const = 0;
};
struct MockedNetwork: public INetwork {
public:
    MOCK_METHOD(std::exception_ptr, getExceptionPtr, (), (const override));
};
// simplified system
class System {
public:
    System(INetwork& network): _network{network} {}
    void run() {
        // some complex logic
        std::exception_ptr exPtr = _network.getExceptionPtr();
        if (exPtr) {
            // error handling, or just rethrow
            std::rethrow_exception(exPtr);
        }
    }
private:
    INetwork& _network;
};

然后我想针对以下场景测试我的代码

Whenever Network reports an error through exception_ptr, System shall rethrow this exception

所以我有这个小的 gtest 测试用例:

#include <stdexcept>
#include <gtest/gtest.h>

struct MyException: public std::runtime_error {
    MyException(): std::runtime_error("MyException") {}
};

TEST(Demo, demo) {
    MockedNetwork mockedNet;
    EXPECT_CALL(mockedNet, getExceptionPtr()).WillRepeatedly([]() -> std::exception_ptr{
        return nullptr;  // this is OK, but I want to simulate an error, not error-free run
        // return new MyException;  // this doesn't compile, and anyway seems like a bad idea
    });
    System sut(mockedNet);
    ASSERT_THROW(sut.run(), MyException);
}

如何模拟我的模拟网络返回 std::exception_ptr 的情况，其中包含指向可以重新抛出的自定义异常的指针？

Answer 1

std::make_exception_ptr :

std::exception_ptr e = std::make_exception_ptr(MyException{});