ExclusiveTaskQueue with tests

ExclusiveTaskQueue.cs

    public class ExclusiveTaskQueue
    {
        public ConcurrentExclusiveSchedulerPair _schedulerPair;
        public static TaskFactory _exclusiveTaskFactory;

        public ExclusiveTaskQueue()
        {
            _schedulerPair = new ConcurrentExclusiveSchedulerPair();
            _exclusiveTaskFactory = new TaskFactory(_schedulerPair.ExclusiveScheduler);
        }

        public Task RunExclusively(Action action)
        {
            return _exclusiveTaskFactory.StartNew(action);
        }

        public Task RunExclusively(Func<Task> action)
        {
            return _exclusiveTaskFactory.StartNew(action).Unwrap();
        }
    }

    [TestClass]
    public class ExclusiveTaskQueueTest
    {
        [TestMethod]
        public void TwoTasks_DoesNotOverlap()
        {
            var queue = new ExclusiveTaskQueue();
            var clock = new Clock();
            clock.Init();
            queue.RunExclusively(() => clock.StopAfter(250, 0));
            queue.RunExclusively(() => clock.StopAfter(250, 1));

            Task.Delay(750).Wait();
            Assert.IsTrue(clock.StartTime[0] < 250, "First start time was " + clock.StartTime[0] + "ms");
            Assert.IsTrue(clock.StartTime[1] > 250, "Second start time was " + clock.StartTime[1] + "ms");
            Assert.IsTrue(clock.EndTime[0] > 250, "First end time was " + clock.EndTime[0] + "ms");
            Assert.IsTrue(clock.EndTime[1] > 500, "Second end time was " + clock.EndTime[1] + "ms");
        }
    }

    internal class Clock
    {
        private static long _testStart;
        internal long[] EndTime = new long[2];
        internal long[] StartTime = new long[2];

        public async Task StopAfter(long ms, int ix)
        {
            StartTime[ix] = Environment.TickCount - _testStart;
            await Task.Delay((int)ms);
            EndTime[ix] = Environment.TickCount - _testStart;
        }

        public void Init()
        {
            _testStart = Environment.TickCount;
            for (int i = 0; i < 2; i++)
            {
                EndTime[i] = -1;
                StartTime[i] = -1; 
            }
        }
    }