RowKeySet set1 = new TestPathSet();
RowKeySet set2 = new TestPathSet();
_add(set1, _011, _2, _20);
set2.add(_0);
set2.addAll(set1);
_testInSet(set1, _011, _2, _20);
_testNotInSet(set1, _0);
_testInSet(set2, _0, _011, _2, _20);
// test with set1 having default=true: