TaskQueueTestHelper.java

/*
 * Copyright (c) 2015-present, Parse, LLC.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 */
package com.parse;

import java.util.ArrayList;
import java.util.List;

import bolts.Continuation;
import bolts.Task;
import bolts.TaskCompletionSource;

/**
 * Helper class to step through a {@link TaskQueue}.
 *
 * {@link #enqueue()} and {@link #dequeue()} works as FIFO list that enqueues an unresolved
 * {@link Task} to the end of the {@link TaskQueue} and resolves the first {@link Task}.
 */
public class TaskQueueTestHelper {

  private final Object lock = new Object();
  private final TaskQueue taskQueue;
  private final List<TaskCompletionSource<Void>> pendingTasks = new ArrayList<>();

  public TaskQueueTestHelper(TaskQueue taskQueue) {
    this.taskQueue = taskQueue;
  }

  /**
   * Pauses the {@link TaskQueue} by enqueuing an unresolved {@link Task} to it.
   */
  public void enqueue() {
    synchronized (lock) {
      final TaskCompletionSource<Void> tcs = new TaskCompletionSource();
      taskQueue.enqueue(new Continuation<Void, Task<Void>>() {
        @Override
        public Task<Void> then(Task<Void> task) throws Exception {
          return tcs.getTask();
        }
      });
      pendingTasks.add(tcs);
    }
  }

  /**
   * Resumes the {@link TaskQueue} by resolving the first {@link Task}.
   */
  public void dequeue() {
    synchronized (lock) {
      TaskCompletionSource<Void> tcs = pendingTasks.remove(0);
      tcs.setResult(null);
    }
  }
}