def drag_slider(self, slider):
        ''' Click *slider*, drag from one side to the other, release mouse
        button repeat to restore inital state'''
        position = self.get_slider_position(slider)
        QTest.mouseMove(slider, pos=position.topLeft())
        QTest.mousePress(slider, Qt.LeftButton)
        QTest.mouseMove(slider, pos=position.bottomRight())
        QTest.mouseRelease(slider, Qt.LeftButton)
        QTest.mousePress(slider, Qt.LeftButton)
        QTest.mouseMove(slider, pos=position.topLeft())
        QTest.mouseRelease(slider, Qt.LeftButton)