@Test public void backup_1() {

    DatasetGraph dsg = DatabaseMgr.connectDatasetGraph(dir);
    Txn.executeWrite(dsg, ()-> {
        dsg.add(quad2);
        dsg.add(quad1);
    });
    String file1 = DatabaseMgr.backup(dsg);
    DatasetGraph dsg2 = RDFDataMgr.loadDatasetGraph(file1);
    Txn.executeRead(dsg, ()-> {
        assertTrue(dsg.contains(quad1));
        assertEquals(2, dsg.getDefaultGraph().size());
        assertTrue(dsg2.getDefaultGraph().isIsomorphicWith(dsg.getDefaultGraph()));
    });
    String file2 = DatabaseMgr.backup(dsg);
    assertNotEquals(file1, file2);
}