guava/src/com/google/common/collect/MinMaxPriorityQueue.java
@VisibleForTesting
  boolean isIntact() {
    for (int i = 1; i < size; i++) {
      if (!heapForIndex(i).verifyIndex(i)) {
        return false;
      }
    }
    return true;
  }
@VisibleForTesting
  boolean isIntact() {
    for (int i = 1; i < size; i++) {
      if (!heapForIndex(i).verifyIndex(i)) {
        return false;
      }
    }
    return true;
  }
Returns {@code true} if the MinMax heap structure holds. This is only used in testing.

<p>TODO(kevinb): move to the test class?