Qt event loop and unit testing?

Question

I\'we started experimenting with unit testing in Qt and would like to hear comments on a scenario that involves unit testing signals and slots.

Here is an example:

Answer 1

Good question. Main issues I've hit are (1) needing to let app do app.exec() yet still close-at-end to not block automated builds and (2) needing to ensure pending events get processed before relying on the result of signal/slot calls.

For (1), you could try commenting out the app.exec() in main(). BUT then if someone has FooWidget.exec() in their class that you're testing, it's going to block/hang. Something like this is handy to force qApp to exit:

int main(int argc, char *argv[]) {
    QApplication a( argc, argv );   

    //prevent hanging if QMenu.exec() got called
    smersh().KillAppAfterTimeout(300);

    ::testing::InitGoogleTest(&argc, argv);
    int iReturn = RUN_ALL_TESTS(); 
    qDebug()<<"rcode:"< timer(new QTimer);
  timer->setSingleShot(true);
  bool ok = timer->connect(timer.data(),SIGNAL(timeout()),qApp,SLOT(quit()),Qt::QueuedConnection);
  timer->start(secs * 1000); // N seconds timeout
  timer.take()->setParent(qApp);
  return ok;
}

For (2), basically you have to coerce QApplication into finishing up the queued events if you're trying to verify things like QEvents from Mouse + Keyboard have expected outcome. This FlushEvents<>() method is helpful:

template  struct FlushEvents {     
 FlushEvents() {
 int n = 0;
 while(++n<20 &&  qApp->hasPendingEvents() ) {
   QApplication::sendPostedEvents();
   QApplication::processEvents(QEventLoop::AllEvents);
   YourThread::microsec_wait(100);
 }
 YourThread::microsec_wait(1*1000);
} };

Usage example below. "dialog" is instance of MyDialog. "baz" is instance of Baz. "dialog" has a member of type Bar. When a Bar selects a Baz, it emits a signal; "dialog" is connected to the signal and we need to make sure the associated slot has gotten the message.

void Bar::select(Baz*  baz) {
  if( baz->isValid() ) {
     m_selected << baz;
     emit SelectedBaz();//<- dialog has slot for this
}  }    

TEST(Dialog,BarBaz) {  /**/
dialog->setGeometry(1,320,400,300); 
dialog->repaint();
FlushEvents<>(); // see it on screen (for debugging)

//set state of dialog that has a stacked widget
dialog->setCurrentPage(i);
qDebug()<<"on page: "
        <();  // Now dialog is drawn on page i 

dialog->GetBar()->select(baz); 
FlushEvents<>(); // *** without this, the next test
                 //           can fail sporadically.

EXPECT_TRUE( dialog->getSelected_Baz_instances()
                                 .contains(baz) );
/**/
}