test: add unit test for remove micro app insights extension (#435)

src/Arcus.Observability.Tests.Unit/Telemetry/AzureFunctions/Fixture/ApplicationInsightsLoggerProvider.cs

@@ -0,0 +1,11 @@
+using Microsoft.Extensions.Logging;
+
+namespace Arcus.Observability.Tests.Unit.Telemetry.AzureFunctions.Fixture
+{
+    /// <summary>
+    /// Represents a dummy class with the expected name to be removed by the <see cref="ILoggingBuilderExtensions.RemoveMicrosoftApplicationInsightsLoggerProvider"/>.
+    /// </summary>
+    public class ApplicationInsightsLoggerProvider
+    {
+    }
+}

src/Arcus.Observability.Tests.Unit/Telemetry/AzureFunctions/ILoggerBuilderExtensionsTests.cs

@@ -1,4 +1,5 @@
-using Arcus.Observability.Tests.Unit.Telemetry.AzureFunctions.Fixture;
+using System;
+using Arcus.Observability.Tests.Unit.Telemetry.AzureFunctions.Fixture;
 using Microsoft.Azure.WebJobs.Script.Diagnostics;
 using Microsoft.Extensions.DependencyInjection;
 using Moq;
@@ -7,6 +8,7 @@
 
 namespace Arcus.Observability.Tests.Unit.Telemetry.AzureFunctions
 {
+    // ReSharper disable once InconsistentNaming
     public class ILoggerBuilderExtensionsTests
     {
         [Fact]
@@ -28,5 +30,31 @@ public void ClearProvidersExceptFunctions_WithLoggerBuilderContainingProviders_R
             Assert.Equal(2, services.Count);
             Assert.All(services, desc => Assert.NotEqual(typeof(TestLoggerProvider), desc.ImplementationType));
         }
+
+        [Fact]
+        public void RemoveMicrosoftApplicationInsightsLoggerProvider_WithLoggerBuilderContainingProvider_RemovesProvider()
+        {
+            // Arrange
+            var services = new ServiceCollection();
+            services.AddSingleton<ApplicationInsightsLoggerProvider>();
+
+            // Act
+            services.AddLogging(logging => logging.RemoveMicrosoftApplicationInsightsLoggerProvider());
+
+            // Assert
+            Assert.NotEmpty(services);
+            Assert.All(services, desc => Assert.NotEqual(typeof(ApplicationInsightsLoggerProvider), desc.ImplementationType));
+        }
+
+        [Fact]
+        public void RemoveMicrosoftApplicationInsightsLoggerProvider_WithoutExpectedLoggerProvider_Fails()
+        {
+            // Arrange
+            var services = new ServiceCollection();
+
+            // Act / Assert
+            Assert.ThrowsAny<InvalidOperationException>(() =>
+                services.AddLogging(logging => logging.RemoveMicrosoftApplicationInsightsLoggerProvider()));
+        }
     }
 }