@Test public void testNotSingleElement() throws Exception {
        IntervalSet vocabulary = IntervalSet.of(1,1000);
        vocabulary.add(2000,3000);
        IntervalSet s = IntervalSet.of(50,50);
        String expecting = "{1..49, 51..1000, 2000..3000}";
        String result = (s.complement(vocabulary)).toString();
        assertEquals(expecting, result);
    }
Public default constructor used by TestRig
tool-testsuite/test/org/antlr/v4/test/tool/TestIntervalSet.java