@Before
  public void setUp() throws IOException {
    db = new ImpermanentGraphDatabase();
    engine = new ExecutionEngine(db);
    Transaction tx = db.beginTx();
    andreasNode = db.createNode();
    johanNode = db.createNode();
    michaelaNode = db.getReferenceNode();
    andreasNode.setProperty("name", "Andreas");
    johanNode.setProperty("name", "Johan");
    michaelaNode.setProperty("name", "Michaela");

    index(andreasNode);
    index(johanNode);
    index(michaelaNode);

    tx.success();
    tx.finish();
  }
 public NodeRepresentation getReferenceNode() {
   return new NodeRepresentation(graphDb.getReferenceNode());
 }