arithmeticPostAggregator = new ArithmeticPostAggregator("add", "+", postAggregatorList);
Comparator comp = arithmeticPostAggregator.getComparator();
Object before = arithmeticPostAggregator.compute(metricValues);
agg.aggregate();
agg.aggregate();
agg.aggregate();
metricValues.put(agg.getName(), agg.get());
Object after = arithmeticPostAggregator.compute(metricValues);
Assert.assertEquals(-1, comp.compare(before, after));
Assert.assertEquals(0, comp.compare(before, before));