What's the best way to test the ChatBot with Amazon Lex?

We have designed and built a ChatBot app with the latest Amazon Lex and I am trying to find a more cost-effective way to test the ChatBot.

We have done some unit tests at a low level to check and validate the bot-definition file to ensure the ChatBot can be launched. Now we can't find a quick way to test the chat flow and automate the tests. All we are doing now is still manual process with the given testing panel and check each intent, utterance, and slots and verify the response. Apparently, this is not a productive way and is not quite scalable.

Regression testing is such a pain if we make any breaking changes or adding new functionalities to the existing ChatBot.

Any good suggestions for testing the ChatBot would be much appreciated.