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.runners.direct;
  
  import static org.apache.beam.vendor.guava.v32_1_2_jre.com.google.common.base.Preconditions.checkArgument;
  
  import org.joda.time.Duration;
  import org.joda.time.Instant;
  
  /**
   * A clock that returns a constant value for now which can be set with calls to {@link
   * #set(Instant)}.
   *
   * <p>For uses of the {@link Clock} interface in unit tests.
   */
  class MockClock implements Clock {
  
    private Instant now;
  
    public static MockClock fromInstant(Instant initial) {
      return new MockClock(initial);
    }
  
    private MockClock(Instant initialNow) {
      this.now = initialNow;
    }
  
    public void set(Instant newNow) {
      checkArgument(
          !newNow.isBefore(now),
          "Cannot move MockClock backwards in time from %s to %s",
          now,
          newNow);
      this.now = newNow;
    }
  
    public void advance(Duration duration) {
      checkArgument(
          duration.getMillis() > 0,
          "Cannot move MockClock backwards in time by duration %s",
          duration);
      set(now.plus(duration));
    }
  
    @Override
    public Instant now() {
      return now;
    }
  }
  