@Test public void testIsolatedElements() throws Exception {
		IntervalSet s = new IntervalSet();
		s.add(1);
		s.add('z');
		s.add('\uFFF0');
		String expecting = "{1, 122, 65520}";
        assertEquals(s.toString(), expecting);
    }
Public default constructor used by TestRig
tool-testsuite/test/org/antlr/v4/test/tool/TestIntervalSet.java