This is near the end of this Seq Logging Implementation

Tests/Logging/SeqTelemetryChannelTest.cs

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+using Autofac;
+using Microsoft.ApplicationInsights;
+using Microsoft.ApplicationInsights.Channel;
+using Microsoft.ApplicationInsights.DataContracts;
+using PlanTempus.Core.Logging;
+using PlanTempus.Core.Telemetry;
+
+namespace PlanTempus.Tests.Logging
+{
+    [TestClass]
+    public class SeqTelemetryChannelTest : TestFixture
+    {
+        private IMessageChannel<ITelemetry> _messageChannel;
+        TelemetryClient _telemetryClient;
+        private SeqBackgroundService _service;
+        private CancellationTokenSource _cts;
+
+        [TestInitialize]
+        public void SetupThis()
+        {
+            //it is important to use the same MessageChannel as the BackgroundService uses
+            //we know that IMessageChannel<ITelemetry> _messageChannel; is registered via Autofac and manually injected into SeqBackgroundService
+            //so we can get it by calling the Autofac Container in this test.
+
+            _messageChannel = Container.Resolve<IMessageChannel<ITelemetry>>();
+            _service = Container.Resolve<SeqBackgroundService>();
+            _telemetryClient = Container.Resolve<TelemetryClient>();
+
+            _cts = new CancellationTokenSource();
+        }
+
+        [TestMethod]
+        public async Task Messages_ShouldBeProcessedFromQueue()
+        {
+            await _service.StartAsync(_cts.Token);
+
+            for (int i = 0; i < 5; i++)
+            {
+                var eventTelemetry = new EventTelemetry
+                {
+                    Name = "Test Event 3",
+                    Timestamp = DateTimeOffset.UtcNow
+                };
+
+                eventTelemetry.Properties.Add("TestId", Guid.NewGuid().ToString());
+                eventTelemetry.Metrics.Add("TestMetric", 42.0);
+
+                //we don't write to the  _messageChannel.Writer.WriteAsync(eventTelemetry);, but the TelemetryClient which is configured to use SeqTelemetryChannel
+                _telemetryClient.TrackEvent(eventTelemetry);
+            }
+
+            // wait for processing
+            await Task.Delay(5000);
+
+            //_cts.Cancel();
+            await _service.StopAsync(CancellationToken.None);
+
+
+            bool hasMoreMessages = await _messageChannel.Reader.WaitToReadAsync();
+            Assert.IsFalse(hasMoreMessages, "Queue should be empty after 5 seconds");
+        }
+
+       
+        [TestCleanup]
+        public void Cleanup()
+        {
+            _cts?.Dispose();
+        }
+    }
+}