JUnit testing internal classes

Question

I have an assignment for university that requires me to have all my code within a single *.java file. The problem I am currently dealing with is that I have a couple support classes written within the application so that at least some of the functionality is separated. The thing is, some of those support classes are quite simple, yet have a lot of functionality.

To make my problem clearer, here is the file structure for my main class.

public class Assignment {
  // ...
  protected class UtilClass1 {
    // ...
  }
  protected class UtilClass2 {
    // ...
  }
  // ...
}

My problem now is that I want to write JUnit test cases for these utility classes, as the various inputs I would have to test manually would be very time consuming, and what I really need is just to test the utility classes.

I have managed to write a simple test that tests a bit of functionality within this single line of code. Like so:

  @Before
  public void initAssignment() {
    app = new Assignment();
  }

  @Test
  public void testNumberCreate() {
    assertTrue(app.new Number(new int[] {1,2,3,4,5}).toString().equals("12345"));
  }

In this particular case, Number is one of the support classes I want to test. One problem I'm having is that I don't know how I would store the inner datatype in a variable, because most tests simply can not be a single line of code.

I am aware that I could solve this problem by making all the inner classes static, but I am wondering if there is another way to achieve this without making them static. Also, I would appreciate any cleaner way to test these classes as this is extremely messy.

Answer 1

This works for me:

public class Foo{

    protected class Bar{}

    public static void main(String[] args){
        Foo.Bar bar = (new Foo()).new Bar();
    }
}

No compilation error. You'll then be able to access any accessible method on bar .