    @Test
    public void testInsertAndDeleteData() throws ParseException {


        String queryStr = "PREFIX ns: <http://example.org/ns#> " +
                "INSERT DATA { <http://example/book1>  ns:price  42 }; " +
                "DELETE DATA { GRAPH " + TEST_GRAPH.toString() + " { <http://example/book1>  ns:price  42 } }";
        SparqlPreParser parser;
        parser = new SparqlPreParser(this.graphStore);
        Set<IRI> referredGraphs = parser.getReferredGraphs(queryStr, DEFAULT_GRAPH);

        Set<IRI> expected = new HashSet<>();
        expected.add(DEFAULT_GRAPH);
        expected.add(TEST_GRAPH);
        Assert.assertTrue(referredGraphs.containsAll(expected));
    }