private void createGraph4() {
    StreamApplicationDescriptorImpl appDesc = mock(StreamApplicationDescriptorImpl.class);
    graph4 = new JobGraph(new MapConfig(), appDesc);

    JobNode n1 = graph4.getOrCreateJobNode("1", "1");

    graph4.addInputStream(genStream(), n1);
    graph4.addIntermediateStream(genStream(), n1, n1);
  }
graph4 is a graph of single-loop node
1<->1
samza-core/src/test/java/org/apache/samza/execution/TestJobGraph.java