// default graph: {context2}; named graph: {}
query.setDataset(dataset);
assertFalse(query.ask());
// default graph: {context1, context2}; named graph: {context2}
dataset.addDefaultGraph(context1);
dataset.addNamedGraph(context2);
query.setDataset(dataset);
assertFalse(query.ask());
// default graph: {context1, context2}; named graph: {context1, context2}