public Collection<Integer> getAssignedWorkerIds() {
        Collection<String> childrenKeys = repository.getChildrenKeys(ComputeNode.getInstanceWorkerIdRootNodePath());
        Collection<Integer> result = new LinkedHashSet<>(childrenKeys.size(), 1F);
        for (String each : childrenKeys) {
            String workerId = repository.query(ComputeNode.getInstanceWorkerIdNodePath(each));
            if (null != workerId) {
                result.add(Integer.parseInt(workerId));
            }
        }
        return result;
    }
@Test
    void assertGetUsedWorkerIds() {
        new ComputeNodePersistService(repository).getAssignedWorkerIds();
        verify(repository).getChildrenKeys(ComputeNode.getInstanceWorkerIdRootNodePath());
    }