UA-.NETStandard/tests/Opc.Ua.Server.Tests/ReverseConnectServerTimerTests.cs

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using System;
using System.Collections.Generic;
using System.Threading;
using System.Threading.Tasks;
using Moq;
using NUnit.Framework;
using Opc.Ua.Tests;

namespace Opc.Ua.Server.Tests
{
    /// <summary>
    /// Exercises callbacks already queued when their reverse-connect timer is disposed.
    /// </summary>
    [TestFixture]
    [Category("ReverseConnect")]
    [Parallelizable]
    public sealed class ReverseConnectServerTimerTests
    {
        [TestCase(false)]
        [TestCase(true)]
        public async Task QueuedCallbackAfterShutdownCannotConnectOrRearmAsync(bool dispose)
        {
            var scheduler = new QueuedTimerScheduler();
            using var server = new ReverseConnectServer(NUnitTelemetryContext.Create(), scheduler.Clock.Object);
            server.AddReverseConnection(s_clientUrl);
            Action queuedCallback = scheduler.Callbacks[0];

            if (dispose)
            {
                server.Dispose();
            }
            else
            {
                await server.StopAsync(CancellationToken.None).ConfigureAwait(false);
            }
            queuedCallback();

            Assert.That(scheduler.Timers, Has.Count.EqualTo(1));
            scheduler.Timers[0].Verify(timer => timer.Dispose(), Times.Once);
            Assert.That(server.GetReverseConnections()[s_clientUrl].LastState, Is.EqualTo(ReverseConnectState.Closed));
        }

        [Test]
        public void QueuedCallbackFromRemovedTimerDoesNotReplaceCurrentTimer()
        {
            var scheduler = new QueuedTimerScheduler();
            using var server = new ReverseConnectServer(NUnitTelemetryContext.Create(), scheduler.Clock.Object);
            server.AddReverseConnection(s_clientUrl, enabled: false);
            Action queuedCallback = scheduler.Callbacks[0];

            Assert.That(server.RemoveReverseConnection(s_clientUrl), Is.True);
            server.AddReverseConnection(s_clientUrl, enabled: false);
            queuedCallback();

            Assert.That(scheduler.Timers, Has.Count.EqualTo(2));
            scheduler.Timers[0].Verify(timer => timer.Dispose(), Times.Once);
            scheduler.Timers[1].Verify(timer => timer.Dispose(), Times.Never);
        }

        [Test]
        public void ActiveCallbackSchedulesTheNextAttempt()
        {
            var scheduler = new QueuedTimerScheduler();
            using var server = new ReverseConnectServer(NUnitTelemetryContext.Create(), scheduler.Clock.Object);
            server.AddReverseConnection(s_clientUrl, enabled: false);

            scheduler.Callbacks[0]();

            Assert.That(scheduler.Timers, Has.Count.EqualTo(2));
            scheduler.Timers[0].Verify(timer => timer.Dispose(), Times.Once);
            scheduler.Timers[1].Verify(timer => timer.Dispose(), Times.Never);
            Assert.That(scheduler.DueTimes[0], Is.EqualTo(TimeSpan.FromSeconds(1)));
            Assert.That(scheduler.DueTimes[1],
                Is.EqualTo(TimeSpan.FromMilliseconds(ReverseConnectServer.DefaultReverseConnectInterval)));
        }

        private sealed class QueuedTimerScheduler
        {
            public QueuedTimerScheduler()
            {
                Clock.Setup(clock => clock.CreateTimer(
                    It.IsAny<TimerCallback>(),
                    It.IsAny<object>(),
                    It.IsAny<TimeSpan>(),
                    It.IsAny<TimeSpan>()))
                    .Returns((TimerCallback callback, object state, TimeSpan dueTime, TimeSpan period) =>
                    {
                        Assert.That(period, Is.EqualTo(Timeout.InfiniteTimeSpan));
                        var timer = new Mock<ITimer>();
                        Timers.Add(timer);
                        Callbacks.Add(() => callback(state));
                        DueTimes.Add(dueTime);
                        return timer.Object;
                    });
            }

            public Mock<TimeProvider> Clock { get; } = new();
            public List<Mock<ITimer>> Timers { get; } = [];
            public List<Action> Callbacks { get; } = [];
            public List<TimeSpan> DueTimes { get; } = [];
        }

        private static readonly Uri s_clientUrl = new("opc.tcp://localhost:4840/queued-timer");
    }
}