Question

Initially, I wrote a class (lets call it RangeSet) that operated on an ArrayList of intervals (the interval class defined by me as two Long values). The list was a collection of intervals, there was a void add(Range range) method which checked whether there was an overlap, overwriting, containment or adjacency with intervals already on the list. The point was to hold the list of non-overlaping intervals.

I designed and wrote extensive tests for that class, checking the wide variety of cases that may occur.
It’s a lot of code is what I’m saying.

Now it turns out that (for whatever reason) I had to split that class into two seperate classes – RangeSet will be an abstract class with a couple of useful methods and inherited from it – ArrayRangeSet (holding the collection of intervals in ArrayList) and TreeRangeSet (holding the collection of intervals in a TreeSet). The implementation of add(Range range) method differs a lot between those two.

How shall I inherit tests to avoid redundancy in defining test data?

An example test looks like this:

@Test
void testCase4(){
    RangeSet set = new RangeSet();
    Range r1 = new Range(4, 5);
    Range r2 = new Range(13, 15);
    Range r3 = new Range(19, 22);
    set.add(r1);
    set.add(r2);
    set.add(r3);

    Range testRange = new Range(11,100);
    set.add(testRange);

    assertEquals(2,set.iterator().size());
    assertEquals(new Range(4,5),set.iterator().getAt(0));
    assertEquals(new Range(11,100),set.iterator().getAt(1));
}

I dont know whether I’m being clear: There’s a lot of test data defining and tests for those two classes would look the same. How do I solve that?

EDIT: Is there a way to pass those assert statements to inherited test classes? Afterall, those add methods are supposed to achieve the same goal, albeit by different operations.

Answer 1

I would write a test class for RangeSet, that provides the test data and let the tests of ArrayRangeSet and TreeRangeSet inherit from it. If you provide a mechanism to create instances of ArrayRangeSet and TreeRangeSet in the base test (e.g. an abstract “factory” method), you can put the tests of all methods that are supposed to have the same behavior in both classes into the base test. The test classes ArrayRangeSet and TreeRangeSet contain only tests of “specific” methods.