Assert.assertEquals(plan.getSuccessors(load1).get(0), filter);
Assert.assertEquals(plan.getSuccessors(filter).get(0), join);
Assert.assertEquals(plan.getSuccessors(join).get(0), store);
// run merge filter rule
r = new MergeFilter("MergeFilter");
s = new HashSet<Rule>();
s.add(r);
ls = new ArrayList<Set<Rule>>();
ls.add(s);
optimizer = new MyPlanOptimizer(plan, ls, 3);