PropertyList pl = null;
pl = PropertyList.add ("one", 1.0, pl);
pl = PropertyList.add ("two", 2.0, pl);
pl = PropertyList.add ("three", 3, pl);
assertTrue (pl.lookupNumber("one") == 1.0);
pl = PropertyList.remove ("three", pl);
assertTrue (pl.lookupNumber("three") == 0.0);
pl = PropertyList.add ("color", "red", pl);
assertTrue (pl.lookupObject("color").equals("red"));