Parser Testing Approaches and Tools

There is a website with tickets and my developer write a parser(written in JS), the parser itself is legitimate to the Telegram in the form of a bot. Only 2 commands - /day and /route. Every 15 minutes, Telegram bot will give an answer with existing flights at a given date and route.

In brief about the work:

There is a site - we send a POST request, we receive HTML, and JS parses this HTML, and then gives answers to our bot

There are no requirements for non-functional testing. What types would you recommend producing? Can I somehow use Postman, JMeter, and other testing software?

I am new in non-functional testing, but I'm very interested to carry out some kind of non-functional testing of this functional.