@Test(expectedExceptions = IllegalArgumentException.class)
public void testOverlapCustom() {

    IntervalSet set = new IntervalSet();
    Assert.assertTrue(set.add(new Interval(1.0, 2.0)));
    Assert.assertTrue(set.add(new Interval(3.0, 4.0)));
    Assert.assertTrue(set.add(new Interval(2.0, 2.0)));
    set.add(new Interval(2.0, 4.0));
}