How to write an automated test for thread safety

Question

I have a class which is not thread safe:

class Foo { 
    /* Abstract base class, code which is not thread safe */ 
};

Moreover, if you hav

Answer 1

So far I've written the following code. Sometimes it works and sometimes the test fails, since the Sleep is not enough for running all threads.

//! Give some time to the other threads
static void YieldThread()
{
#ifdef _WIN32
    Sleep(10);
#endif //_WIN32
}

class FooWithMutex: public Foo {
public:
    QMutex m_mutex;
    virtual void someFunc()
    {
        QMutexLocker(&m_mutex);
    }
    virtual void anotherFunc()
    {
        QMutexLocker(&m_mutex);
    }
};

class ThreadThatCallsFooFunc1: public QThread {
public:
    ThreadThatCallsFooFunc1( FooWrapper& fooWrapper )
        : m_fooWrapper(fooWrapper) {}

    virtual void run()
    {
        m_fooWrapper.someFunc();
    }
private:
    FooWrapper& m_fooWrapper;
};

class ThreadThatCallsFooFunc2: public QThread {
public:
    ThreadThatCallsFooFunc2( FooWrapper& fooWrapper )
        : m_fooWrapper(fooWrapper) {}

    virtual void run()
    {
        m_fooWrapper.anotherFunc();
    }
private:
    FooWrapper& m_fooWrapper;
};

TEST(ScriptPluginWrapperTest, CallsFromMultipleThreads)
{
    // FooWithMutex inherits the abstract Foo and adds
    // mutex lock/unlock on each function.
    FooWithMutex fooWithMutex;

    FooWrapper fooWrapper( &fooWithMutex );
    ThreadThatCallsFooFunc1 thread1(fooWrapper);
    ThreadThatCallsFooFunc2 thread2(fooWrapper);

    fooWithMutex.m_mutex.lock();
    thread1.start(); // Should block

    YieldThread();
    ASSERT_FALSE( thread1.isFinished() );

    thread2.start(); // Should finish immediately
    YieldThread();
    ASSERT_TRUE( thread2.isFinished() );

    fooWithMutex.m_mutex.unlock();

    YieldThread();
    EXPECT_TRUE( thread1.isFinished() );
}