WorkflowDag emptyDag = new WorkflowDag();
WorkflowContext three = new WorkflowContext();
three.setWorkflowDag(emptyDag);
WorkflowDag mergedDag = new WorkflowDag();
mergedDag.addEntry(getEntry("a", "b", "c", "d"));
mergedDag.addEntry(getEntry("b", "d"));
mergedDag.addEntry(getEntry("c", "e"));
assertEquals(mergedDag, MapReduceJobHistoryUpdater.constructMergedDag(one, two));
assertEquals(mergedDag, MapReduceJobHistoryUpdater.constructMergedDag(two, one));