content: /*
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package org.apache.beam.sdk.util;
  
  import static org.junit.Assert.assertEquals;
  import static org.junit.Assert.assertTrue;
  
  import java.util.concurrent.TimeUnit;
  import org.junit.Rule;
  import org.junit.Test;
  import org.junit.runner.RunWith;
  import org.junit.runners.JUnit4;
  
  /** Tests for {@link FastNanoClockAndSleeper}. */
  @RunWith(JUnit4.class)
  public class FastNanoClockAndSleeperTest {
    @Rule public FastNanoClockAndSleeper fastNanoClockAndSleeper = new FastNanoClockAndSleeper();
  
    @Test
    public void testClockAndSleeper() throws Exception {
      long sleepTimeMs = TimeUnit.SECONDS.toMillis(30);
      long sleepTimeNano = TimeUnit.MILLISECONDS.toNanos(sleepTimeMs);
      long fakeTimeNano = fastNanoClockAndSleeper.nanoTime();
      long startTimeNano = System.nanoTime();
      fastNanoClockAndSleeper.sleep(sleepTimeMs);
      long maxTimeNano = startTimeNano + TimeUnit.SECONDS.toNanos(1);
      // Verify that actual time didn't progress as much as was requested
      assertTrue(System.nanoTime() < maxTimeNano);
      // Verify that the fake time did go up by the amount requested
      assertEquals(fakeTimeNano + sleepTimeNano, fastNanoClockAndSleeper.nanoTime());
    }
  }
  