def METHOD_NAME(self):  # insert and delete
    self.text.insert('1.0', 'hello')
    self.text.insert('1.3', '1\n2\n3\n4\n5')
    self.assertEqual(self.text.get('1.0', 'end'), 'hel1\n2\n3\n4\n5lo\n')
    self.text.delete('1.3', '5.1')
    self.assertEqual(self.text.get('1.0', 'end'), 'hello\n')