Hi Satyam,
ATS is a low code testing tool specifically built for Mendix https://docs.mendix.com/addons/ats-addon/
Hope this helps
If you want free options I would recommend either Selenium or LoadRunner (this is a load testing tool, but it's easy to record scenario's and free if you run a single concurrent session, so it can be used for your kind of testing).
i think Jmeter is also a good chioce.