Unit Testing Web page handlers in Tornado

I'm sorry if this is a repeat, or just a dumb question, but I'm currently interning at a small startup whose product is a web page. I thought that creating a system to test components would be extremely useful for interns in the future so that they could understand what is going on under the hood and not have to debug in the dark.

Here is my issue - I've been looking through Tornado unit testing and Mock documentation, and it is all very, very confusing.

I want to write a program that would "click" a button on a page, then point out what is happening in the backend (a user's information in mongodb is being updated, information is being passed to a certain mail handler so that the information submitted on the page is emailed to someone, etc.)

How do I make a testing system that can go through buttons / other functionality on the web page, and also display what is happening on the back end? If code would help then I will ask permission to upload it. I am wondering why there seems to be no tutorials and little information on how to test.