private Config getConfig() {
    HashMap<String, String> configMap = new HashMap<>();
    configMap.put(JobConfig.JOB_NAME, "test-job");
    configMap.put(JobConfig.JOB_ID, "1");
    return new MapConfig(configMap);
  }
the task assignment looks like the following:

input1 -----> task0, task1 -----> int1
                                   ^
input2 ------> task1, task2--------|
                                   v
input3 ------> task1 -----------> int2
samza-core/src/test/java/org/apache/samza/operators/impl/TestOperatorImplGraph.java