/**
   * Tests whether an algebra expression gives the same results when run both with and without a
   * given optimizer
   *
   * @param algStr Algebra
   * @param ds Dataset
   * @param opt Optimizer
   * @param expected Expected number of results
   */
  public static void testAsAlgebra(String algStr, Dataset ds, Symbol opt, int expected) {
    Op op = SSE.parseOp(algStr);
    List<String> vars = new ArrayList<>();
    for (Var v : OpVars.visibleVars(op)) {
      vars.add(v.getName());
    }

    // Track current state
    boolean isEnabled = ARQ.isTrue(opt);
    boolean isDisabled = ARQ.isFalse(opt);

    try {
      // Run first without optimization
      ARQ.set(opt, false);
      QueryEngineMain engine =
          new QueryEngineMain(op, ds.asDatasetGraph(), BindingFactory.binding(), ARQ.getContext());
      QueryIterator iter =
          engine.eval(op, ds.asDatasetGraph(), BindingFactory.binding(), ARQ.getContext());
      ResultSetRewindable rs =
          ResultSetFactory.makeRewindable(
              new ResultSetStream(vars, ModelFactory.createDefaultModel(), iter));
      if (expected != rs.size()) {
        System.err.println("Non-optimized results not as expected");
        TextOutput output = new TextOutput((SerializationContext) null);
        output.format(System.out, rs);
        rs.reset();
      }
      Assert.assertEquals(expected, rs.size());
      iter.close();

      // Run with optimization
      ARQ.set(opt, true);
      engine =
          new QueryEngineMain(op, ds.asDatasetGraph(), BindingFactory.binding(), ARQ.getContext());
      QueryIterator iterOpt =
          engine.eval(op, ds.asDatasetGraph(), BindingFactory.binding(), ARQ.getContext());
      ResultSetRewindable rsOpt =
          ResultSetFactory.makeRewindable(
              new ResultSetStream(vars, ModelFactory.createDefaultModel(), iterOpt));
      if (expected != rsOpt.size()) {
        System.err.println("Optimized results not as expected");
        TextOutput output = new TextOutput((SerializationContext) null);
        output.format(System.out, rsOpt);
        rsOpt.reset();
      }
      Assert.assertEquals(expected, rsOpt.size());
      iterOpt.close();

      Assert.assertTrue(ResultSetCompare.isomorphic(rs, rsOpt));
    } finally {
      // Restore previous state
      if (isEnabled) {
        ARQ.set(opt, true);
      } else if (isDisabled) {
        ARQ.set(opt, false);
      } else {
        ARQ.unset(opt);
      }
    }
  }
  /**
   * Tests whether a query gives the same results when run both with and without a given optimizer
   *
   * @param queryStr Query
   * @param ds Dataset
   * @param opt Optimizer
   * @param expected Expected number of results
   */
  public static void test(String queryStr, Dataset ds, Symbol opt, int expected) {
    Query q = QueryFactory.create(queryStr);

    if (!q.isSelectType()) Assert.fail("Only SELECT queries are testable with this method");

    Op op = Algebra.compile(q);
    // Track current state
    boolean isEnabled = ARQ.isTrue(opt);
    boolean isDisabled = ARQ.isFalse(opt);

    try {
      // Run first without optimization
      ARQ.set(opt, false);
      ResultSetRewindable rs;
      try (QueryExecution qe = QueryExecutionFactory.create(q, ds)) {
        rs = ResultSetFactory.makeRewindable(qe.execSelect());
        if (expected != rs.size()) {
          System.err.println("Non-optimized results not as expected");
          TextOutput output = new TextOutput((SerializationContext) null);
          output.format(System.out, rs);
          rs.reset();
        }
        Assert.assertEquals(expected, rs.size());
      }

      // Run with optimization
      ARQ.set(opt, true);
      ResultSetRewindable rsOpt;
      try (QueryExecution qeOpt = QueryExecutionFactory.create(q, ds)) {
        rsOpt = ResultSetFactory.makeRewindable(qeOpt.execSelect());
        if (expected != rsOpt.size()) {
          System.err.println("Optimized results not as expected");
          TextOutput output = new TextOutput((SerializationContext) null);
          output.format(System.out, rsOpt);
          rsOpt.reset();
        }
        Assert.assertEquals(expected, rsOpt.size());
      }
      Assert.assertTrue(ResultSetCompare.isomorphic(rs, rsOpt));
    } finally {
      // Restore previous state
      if (isEnabled) {
        ARQ.set(opt, true);
      } else if (isDisabled) {
        ARQ.set(opt, false);
      } else {
        ARQ.unset(opt);
      }
    }
  }