Java unit test for void methods

Question

First of all I would like to apologise about my language skill, but my mother language isn't english.

I have got a little source code, which is:

public void hello(List l){    
    switch (l.get(0) {    
    case "hello":    
         System.out.println("Hello!");    
    case "world":    
        System.out.println("World");    
        break;    
    }    
}

And I have to write a unit test, which can testing about this code. But my skill is not enough about it. Could somebody help me please? Some example or book or something. I don't know how can I starting it!

I am appreciate.

Thanks

Answer 1

You can not obviously test if the method returns correct value if it is 'void'. However you can test whether it throws any exception or not. If you want to test the computation you need to refactor the code such that the computation is a separate method that returns a value.

Answer 2

You should break up your code into two methods - one prints the results of the second, and the second can be easily unit tested.