public static ContainerModel createContainerModel(String containerId, int[] partitions) {
    Map<TaskName, TaskModel> tasks = new HashMap<>();
    for (int partition : partitions) {
      tasks.put(getTaskName(partition), getTaskModel(partition));
    }
    return new ContainerModel(containerId, tasks);
  }
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