[Boost-users] [test/signals] trying test thread safe signals with the boost unit test framework

From: Richard Dingwall (rdingwall_at_[hidden])
Date: 2008-06-06 23:14:15

Hi guys,

Using the boost unit test framework, I'm trying to test a simple
scenario: when a person's name is set, their 'updated' signal is
triggered.

Here's my person class:

class person
{
public:
        
        person() : name_() {};
        
        void name(const std::string & name)
        {
                name_ = name;
                updated(*this);
        };
        
        boost::signal<void(const person & person)> updated;

private:
        std::string name_;
};

To test this, I've created a mock handler for the updated event. In
it's destructor, it checks has been called (and also with the correct
subject):

struct mock_handler
{
        mock_handler(const person & subject) :
                has_been_called_(false), subject_(subject) {};
        
        // Handler.
        void operator()(const person & subject)
        {
                BOOST_TEST_MESSAGE("in mock_handler::operator()");
                
                has_been_called_ = true;
                BOOST_CHECK_EQUAL(&subject == &subject_, true);
        };
        
        // This handler must be called before it goes out of scope.
        ~mock_handler()
        {
                BOOST_TEST_MESSAGE("in mock_handler::~mock_handler()");
                
                BOOST_CHECK_EQUAL(has_been_called_, true);
        };

private:
        bool has_been_called_;
        const person & subject_;
};
And then writing my test case to use it:

BOOST_AUTO_TEST_CASE(setting_name_triggers_update_signal)
{
        BOOST_TEST_MESSAGE("entered test");
        
        person subject;
        mock_handler handler(subject);
        
        subject.updated.connect(handler);
        
        subject.name("Richard");
        
        BOOST_TEST_MESSAGE("exiting test");
}

Unfortunately, when this code runs, it produces the following output:

Running 1 test case...
entered test
in mock_handler::~mock_handler()
test.cpp(46): error in "setting_name_triggers_update_signal": check
has_been_called_ == true failed [0 != 1]
in mock_handler::~mock_handler()
test.cpp(46): error in "setting_name_triggers_update_signal": check
has_been_called_ == true failed [0 != 1]
in mock_handler::~mock_handler()
test.cpp(46): error in "setting_name_triggers_update_signal": check
has_been_called_ == true failed [0 != 1]
in mock_handler::operator()
exiting test
in mock_handler::~mock_handler()
test.cpp(46): error in "setting_name_triggers_update_signal": check
has_been_called_ == true failed [0 != 1]
in mock_handler::~mock_handler()

*** 4 failures detected in test suite "tests"

I'm not sure what's going on here, or why mock_handler's destructor is
being called 4 extra times.

Can anyone shed some light as to why this might be happening?

Cheers,

Rich