Dataset ds = graphLocation.getDataset() ;
Graph g1 = ds.getDefaultModel().getGraph() ;
// Sometimes, under windows, deleting the files by
// graphLocation.clearDirectory does not work.
// Needed for safe tests on windows.
g1.clear() ;
Graph g2 = ds.getNamedModel("http://example/").getGraph() ;
g2.add(new Triple(n0,n1,n2) ) ;
assertTrue(g2.contains(n0,n1,n2) ) ;
assertFalse(g1.contains(n0,n1,n2) ) ;