public boolean statsHaveChanged() {
        if (!aggregatedStats.hasUpdatesFromAllDistributors()) {
            return false;
        }
        for (ContentNodeStats contentNodeStats : aggregatedStats.getStats()) {
            int nodeIndex = contentNodeStats.getNodeIndex();
            boolean currValue = mayHaveMergesPendingInGlobalSpace(nodeIndex);
            Boolean prevValue = prevMayHaveMergesPendingInGlobalSpace(nodeIndex);
            if (prevValue != null) {
                if (prevValue != currValue) {
                    return true;
                }
            } else {
                return true;
            }
        }
        return false;
    }
@Test
    void stats_have_not_changed_if_not_all_distributors_are_updated() {
        Fixture f = Fixture.empty();
        assertFalse(f.statsHaveChanged());
    }