There are more and more options popping up to run tests for Mendix app. It depends on how much effort you want to put in to get that suite filled and running.
If you’re looking for something that is powerful and inexpensive you can check out Selenium here: Selenium
Official how-to from Mendix on how to start using Selenium for your project: Mendix + Selenium
A lot of the tools out there are based on Selenium, but add in a layer of convenience and tracking for you. If you’re willing to put in the work you, Selenium can be a powerful testing tool for you.
Hope this helps!