assertTrue(isVisible(button_1));
assertFalse(isVisible(button_2));
// double click handle of "button_1"
{
Rectangle bounds = panel.getWidgetHandles().get(1).getBounds();
Point handleCenter = bounds.getCenter();
canvas.moveTo(panel, handleCenter.x, handleCenter.y).doubleClick();
}
// now "button_2" is visible
assertFalse(isVisible(button_1));
assertTrue(isVisible(button_2));