private static CompletableFuture<Void> failedFuture(Throwable ex) {
    Preconditions.checkNotNull(ex);
    CompletableFuture<Void> failedFuture = new CompletableFuture<>();
    failedFuture.completeExceptionally(ex);

    return failedFuture;
  }
Package private setter for private var operatorImplGraph to be used in TestStreamOperatorTask tests.
samza-core/src/main/java/org/apache/samza/task/StreamOperatorTask.java