code: def test_get_columns_returns_all_columns(self):
      api_handler = Mock(RocketChatHandler)
      messages_table = RocketChatMessagesTable(api_handler)
      # Order matters.
      expected_columns = [
          "id",
          "room_id",
          "bot_id",
          "text",
          "username",
          "name",
          "sent_at",
      ]
      self.assertListEqual(
          messages_table.get_columns(), expected_columns
      )
  
file_path: mindsdb/tests/handler_tests/test_rocket_chat_handler.py
imports: from mindsdb.integrations.handlers.rocket_chat_handler.rocket_chat_tables import RocketChatMessagesTable
  from mindsdb.integrations.handlers.rocket_chat_handler.rocket_chat_handler import RocketChatHandler
  from mindsdb_sql.parser import ast
  from mindsdb_sql.parser.ast.select.star import Star
  from mindsdb_sql.parser.ast.select.identifier import Identifier
  from unittest.mock import Mock
  import pandas
  import unittest
label_desc: Use image node_id 1 for calling the RocketChatMessagesTableTest obj's underlying member method code with example usage: obj.test_get_columns_returns_all_columns() without return types