How do I test Drag-and-Drop in Qt?

Question

Python

I have a GUI written in PyQt. It actively uses drag-and-drop from one widget to another (we drag objects from the Item View, drop them onto the Graphics Scene).
I want to test my GUI with QTest.
I write code like this:

QtTest.QTest.mouseMove(self.main_wnd.tree_view.viewport(), constant_rect.center(), 300)
        QtTest.QTest.mousePress(self.main_wnd.tree_view.viewport(), QtCore.Qt.LeftButton, QtCore.Qt.KeyboardModifiers(),
                                constant_rect.center(), 300)

        QtTest.QTest.mouseMove(self.main_wnd._scene_views[None].viewport(), QtCore.QPoint(), 300)

        QtTest.QTest.mouseRelease(self.main_wnd.tree_view.viewport(), QtCore.Qt.LeftButton, QtCore.Qt.KeyboardModifiers(),
                                constant_rect.center(), 300)

However, it was not there: yes, the mouse pointer moves where it should be, the desired element in the Item View is selected, and then moved to the center of my scene. But neither the Drag Event nor the Drop Event, unfortunately, happens there.
I have to ask: how to overcome it?