/*
 * 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.jackrabbit.oak.stats;

import static junit.framework.Assert.assertTrue;

import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;

import org.junit.Test;

public class ClockTest {

    @Test
    public void testClockDrift() throws InterruptedException {
        ScheduledExecutorService executor =
                Executors.newSingleThreadScheduledExecutor();
        try {
            Clock[] clocks = new Clock[] {
                    Clock.SIMPLE,
                    Clock.ACCURATE,
                    new Clock.Fast(executor)
            };

            for (Clock clock : clocks) {
                long drift = clock.getTime() - System.currentTimeMillis();
                assertTrue(Math.abs(drift) < 20); // Windows can have 15ms gaps
            }

            Thread.sleep(100);

            for (Clock clock : clocks) {
                long drift = clock.getTime() - System.currentTimeMillis();
                assertTrue(Math.abs(drift) < 20);
            }
        } finally {
            executor.shutdown();
        }
    }

}
Read performance regression