public static int[] range(int from, int to) {
    int[] values = new int[to - from + 1];
    for (int i = 0; i < values.length; i++) {
      values[i] = from++;
    }
    return values;
  }
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