Testautomation software for school

Our task is to make a testautomation software for school, which should take a Java class as an input and then create a JUnit 5 test automatically without any further input.

So far we have a software, which takes the Java file as an input, and then reads the code of it and also finds out, which methods currently exist in the class.

Now our problem is, that we haven't really worked with JUnit so far. So our problem isn't really a coding problem, it is more of a little knowledge Problem.

So as mentioned, right now we have a software which reads the code of o javaclass and then returns the methods of it since we know that there is a Junit testmethod for every "normal" method for every java class.

So has anyone of you a basic idea of how we could create Junit tests automatically.