How to implement blocking mock function with gmock?

Question

In my project I need to mock a blocking function that runs on a thread, I need it to release the thread few times during the tests with my control, on my command, I want it to be blocked most of the time as the read func is in while loop.

class BlockFuncsIf {
public:
    virtual bool Write(const Msg& msg) = 0;
    virtual bool Read(Msg* msg) = 0;

};

class BlockFuncs: public BlockFuncsIf {
public:
    MOCK_METHOD1(Write, bool(const Msg&));
    MOCK_METHOD1(Read, bool(Msg* msg));
};


class TestedClass {
public:
    MSG msg;
    std::condition_variable cv;
    bool success;

    ...

    bool expectRead() {
        success = true;
        while(success) {
            success = Read(&msg);
            cv.notify_all();
        }
    }

    ...

};

Highly related, if not a dupe: https://stackoverflow.com/questions/10767131/expecting-googlemock-calls-from-another-thread — πάντα ῥεῖ, Nov 29 '20 at 11:46
Thanks @πάνταῥεῖ, I saw this one during my research, it lookss similar but didn't solve my blocking problem. — lior.i, Nov 29 '20 at 11:52

lior.i · Accepted Answer · 2020-11-29T12:08:14.347

The solution I found is to wrap the mocked functions and add a semaphore to control the blocking. In this solution I control the semaphore (sem_init, sem_post) from the tests.

Note: I wanted to use std::semaphore but it is available only on c++20 so I used semaphore.h insted, there some other implementation for cpp semaphore avallible if needed: cpp semaphore implementation.

class BlockFuncsIf {
public:
    virtual bool Write(const Msg& msg) = 0;
    virtual bool Read(Msg* msg) = 0;
};

class BlockFuncsMock: public BlockFuncsIf {
public:
    MOCK_METHOD1(Write, bool(const Msg&));
    MOCK_METHOD1(Read, bool(Msg* msg));

    static std::shared_ptr<BlockFuncsMock> _blockFuncsMockObj;
};

std::shared_ptr<BlockFuncsMock> BlockFuncsMock::_blockFuncsMockObj = std::make_shared< BlockFuncsMock >();

class BlockFuncs {
public:
    bool Write(const Msg& msg){
        sem_wait(&SemWriteMutex);
        return BlockFuncsMock::_blockFuncsMockObj->Write(msg);
    }
    bool Read(Msg* msg){
        sem_wait(&SemReadMutex);
        return BlockFuncsMock::_blockFuncsMockObj->Read(msg);
    }
    sem_t SemWriteMutex;
    sem_t SemReadMutex;
};

How to implement blocking mock function with gmock?

1 Answers1