About Tools and testing

I have read all of the Tools and testing article
But I am really distracted about testing for html and css
and A little distracted to js
im using react
I don’t know how to use the test on such things in a REACT, I am aware that REACT uses Babel may slightly reduce the JavaScript test, but there are things that I notice that I am complicated to think about them within the REACT, is there any article that could simplify this?
I have already done a project and work on the following and I did not care about the CSS or HTML test as long as it works in many browsers I have but your article revealed strange and beautiful things how can I take care of this in the future inside Riact