[Tests] Add test to monitor HighPrecisionTickGenerator interval #106

DryWetMidi.Tests/Devices/Clock/TickGenerator/HighPrecisionTickGeneratorTests.cs

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+using System;
+using System.Collections.Generic;
+using System.Diagnostics;
+using System.Threading;
+using Melanchall.DryWetMidi.Devices;
+using NUnit.Framework;
+
+namespace Melanchall.DryWetMidi.Tests.Devices
+{
+    [TestFixture]
+    public sealed class HighPrecisionTickGeneratorTests
+    {
+        #region Test methods
+
+        [Retry(5)]
+        [Test]
+        public void CheckInterval([Values(1, 10, 100)] int interval)
+        {
+            using (var tickGenerator = new HighPrecisionTickGenerator())
+            {
+                var stopwatch = new Stopwatch();
+                var elapsedTimes = new List<long>(150);
+
+                tickGenerator.TickGenerated += (_, __) => elapsedTimes.Add(stopwatch.ElapsedMilliseconds);
+
+                tickGenerator.TryStart(TimeSpan.FromMilliseconds(interval));
+                stopwatch.Start();
+
+                SpinWait.SpinUntil(() => elapsedTimes.Count >= 100);
+                tickGenerator.TryStop();
+                stopwatch.Stop();
+
+                var time = elapsedTimes[0];
+                var maxDelta = 0L;
+                var tolerance = interval * 0.2;
+
+                foreach (var t in elapsedTimes)
+                {
+                    maxDelta = Math.Max(t - time, maxDelta);
+                    time = t;
+                }
+
+                Assert.Less(maxDelta, interval + tolerance, "Max time delta is too big.");
+            }
+        }
+
+        #endregion
+    }
+}