public static TaskModel getTaskModel(int partitionId) {
    return new TaskModel(getTaskName(partitionId),
        new HashSet<>(
            Arrays.asList(new SystemStreamPartition[]{new SystemStreamPartition("System", "Stream", new Partition(partitionId))})),
        new Partition(partitionId));
  }
Note: This is artificial. It makes assumptions about task grouping, changelog partition mapping, etc.
that will likely not be true at runtime, but are not the focus of this test.
samza-core/src/test/java/org/apache/samza/container/mock/ContainerMocks.java