Would testing my Java Servlet be neccessary?

I just wanted to ask if it is necessary to test the java servlet that calls another java method (in another file I might add) to do the bulk of the work.

Like for instance, my java servlet currently only is being used to get parameters and displaying the results of the method that was called in html format. So I am only planning on testing my main java file that does all the work!

I am not very familiar with testing so if there would be specific ways to test this simple Java servlet, please let me know!