There are functions for making touch events (QTest::touchEvent), but it is impossible to use that as those require touch device. QTouchDevice can be created and given to event, but there is no public interface where it could be registered, thus every touch event fails in:

QWindowSystemInterface::handleTouchEvent()

Where it tries to check if touch device is real with:
if (!QTouchDevicePrivate::isRegistered(device)) ...

QWindowSystemInterface::registerTouchDevice() can be used to register touch devices, but that is not public API.