def testAdditionalLayers(self):
QgsProject.instance().clear()
l1 = create_layer('l1')
l2 = create_layer('l2')
QgsProject.instance().addMapLayers([l1, l2])
m = QgsMapLayerComboBox()
self.assertEqual(m.count(), 2)
l3 = create_layer('l3')
l4 = create_layer('l4')
m.setAdditionalLayers([l3, l4])
self.assertEqual(m.count(), 4)
m.setAdditionalItems(['a', 'b'])
self.assertEqual(m.count(), 6)
self.assertEqual(m.itemText(0), 'l1')
self.assertEqual(m.itemText(1), 'l2')
self.assertEqual(m.itemText(2), 'l3')
self.assertEqual(m.itemText(3), 'l4')
self.assertEqual(m.itemText(4), 'a')
self.assertEqual(m.itemText(5), 'b')
m.setAllowEmptyLayer(True)
self.assertEqual(m.count(), 7)
self.assertFalse(m.itemText(0))
self.assertEqual(m.itemText(1), 'l1')
self.assertEqual(m.itemText(2), 'l2')
self.assertEqual(m.itemText(3), 'l3')
self.assertEqual(m.itemText(4), 'l4')
self.assertEqual(m.itemText(5), 'a')
self.assertEqual(m.itemText(6), 'b')
l3.deleteLater()
QCoreApplication.sendPostedEvents(None, QEvent.DeferredDelete)
self.assertEqual(m.count(), 6)
self.assertFalse(m.itemText(0))
self.assertEqual(m.itemText(1), 'l1')
self.assertEqual(m.itemText(2), 'l2')
self.assertEqual(m.itemText(3), 'l4')
self.assertEqual(m.itemText(4), 'a')
self.assertEqual(m.itemText(5), 'b')
l5 = create_layer('l5')
l6 = create_layer('l6')
m.setAdditionalLayers([l5, l6, l4])
self.assertEqual(m.count(), 8)
self.assertFalse(m.itemText(0))
self.assertEqual(m.itemText(1), 'l1')
self.assertEqual(m.itemText(2), 'l2')
self.assertEqual(m.itemText(3), 'l4')
self.assertEqual(m.itemText(4), 'l5')
self.assertEqual(m.itemText(5), 'l6')
self.assertEqual(m.itemText(6), 'a')
self.assertEqual(m.itemText(7), 'b')
m.setAdditionalLayers([l5, l4])
self.assertEqual(m.count(), 7)
self.assertFalse(m.itemText(0))
self.assertEqual(m.itemText(1), 'l1')
self.assertEqual(m.itemText(2), 'l2')
self.assertEqual(m.itemText(3), 'l4')
self.assertEqual(m.itemText(4), 'l5')
self.assertEqual(m.itemText(5), 'a')
self.assertEqual(m.itemText(6), 'b')
QgsProject.instance().removeMapLayers([l1.id(), l2.id()])
self.assertEqual(m.count(), 5)
self.assertFalse(m.itemText(0))
self.assertEqual(m.itemText(1), 'l4')
self.assertEqual(m.itemText(2), 'l5')
self.assertEqual(m.itemText(3), 'a')
self.assertEqual(m.itemText(4), 'b')
