Add Mac implementation of FileChangeTracker.

- Added a LanguageServices Mac test project.
- Added a few tests for the new `DefaultFileChangeTracker`. There's currently an issue with the MonoDevelop.Core binaries we're compiling against which doesn't allow me to unit test other pieces of the class (they depend on instantiating mono develop objects).
- Added IVT from product projects to new mac testing project.

#1789

Razor.sln

@@ -1,6 +1,6 @@
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 15
-VisualStudioVersion = 15.0.26927.3
+VisualStudioVersion = 15.0.27128.0
 MinimumVisualStudioVersion = 15.0.26730.03
 Project("{2150E333-8FDC-42A3-9474-1A3956D46DE8}") = "src", "src", "{3C0D6505-79B3-49D0-B4C3-176F0F1836ED}"
 	ProjectSection(SolutionItems) = preProject
@@ -76,6 +76,8 @@ Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.VisualStudio.Mac.
 EndProject
 Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.VisualStudio.Mac.LanguageServices.Razor", "src\Microsoft.VisualStudio.Mac.LanguageServices.Razor\Microsoft.VisualStudio.Mac.LanguageServices.Razor.csproj", "{95B18DEE-8B45-4CF0-B9F8-CCBAF3B5251A}"
 EndProject
+Project("{9A19103F-16F7-4668-BE54-9A1E7A4F7556}") = "Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test", "test\Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test\Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test.csproj", "{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -306,6 +308,14 @@ Global
 		{95B18DEE-8B45-4CF0-B9F8-CCBAF3B5251A}.Release|Any CPU.Build.0 = Release|Any CPU
 		{95B18DEE-8B45-4CF0-B9F8-CCBAF3B5251A}.ReleaseNoVSIX|Any CPU.ActiveCfg = Release|Any CPU
 		{95B18DEE-8B45-4CF0-B9F8-CCBAF3B5251A}.ReleaseNoVSIX|Any CPU.Build.0 = Release|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.DebugNoVSIX|Any CPU.ActiveCfg = Debug|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.DebugNoVSIX|Any CPU.Build.0 = Debug|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.Release|Any CPU.Build.0 = Release|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.ReleaseNoVSIX|Any CPU.ActiveCfg = Release|Any CPU
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042}.ReleaseNoVSIX|Any CPU.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -339,6 +349,7 @@ Global
 		{FC684D4F-D23C-407C-9C68-E10EF3B38560} = {92463391-81BE-462B-AC3C-78C6C760741F}
 		{FAF9986F-E086-4513-9D52-F7BF5FFCF31D} = {C0CC1E1F-1559-44DE-93A8-63259CEA2AAB}
 		{95B18DEE-8B45-4CF0-B9F8-CCBAF3B5251A} = {3C0D6505-79B3-49D0-B4C3-176F0F1836ED}
+		{B8A3E4CA-D54A-441F-A3BF-E00F060CA042} = {92463391-81BE-462B-AC3C-78C6C760741F}
 	EndGlobalSection
 	GlobalSection(ExtensibilityGlobals) = postSolution
 		SolutionGuid = {0035341D-175A-4D05-95E6-F1C2785A1E26}

build/repo.props

@@ -2,6 +2,7 @@
   <Import Project="dependencies.props" />
 
   <ItemGroup>
+    <ExcludeFromTest Include="$(RepositoryRoot)test\Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test\Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test.csproj" Condition="'$(OS)'!='Windows_NT'" />
     <ExcludeFromTest Include="$(RepositoryRoot)test\Microsoft.VisualStudio.LanguageServices.Razor.Test\Microsoft.VisualStudio.LanguageServices.Razor.Test.csproj" Condition="'$(OS)'!='Windows_NT'" />
     <ExcludeFromTest Include="$(RepositoryRoot)test\Microsoft.AspNetCore.Razor.Test.Common\Microsoft.AspNetCore.Razor.Test.Common.csproj" />
     <ExcludeFromTest Include="$(RepositoryRoot)test\Microsoft.VisualStudio.Editor.Razor.Test\Microsoft.VisualStudio.Editor.Razor.Test.csproj" Condition="'$(OS)'!='Windows_NT'" />

src/Microsoft.CodeAnalysis.Razor.Workspaces/Properties/AssemblyInfo.cs

@@ -9,6 +9,7 @@ using System.Runtime.CompilerServices;
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Editor.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Editor.Razor.Test.Common, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.RazorExtension, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

src/Microsoft.VisualStudio.Editor.Razor/Properties/AssemblyInfo.cs

@@ -5,6 +5,7 @@ using System.Runtime.CompilerServices;
 
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Editor.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.RazorExtension, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/DefaultFileChangeTracker.cs

@@ -0,0 +1,130 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+using MonoDevelop.Core;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor
+{
+    internal class DefaultFileChangeTracker : FileChangeTracker
+    {
+        private readonly ForegroundDispatcher _foregroundDispatcher;
+        private readonly string _normalizedFilePath;
+        private bool _listening;
+
+        public override event EventHandler<FileChangeEventArgs> Changed;
+
+        public DefaultFileChangeTracker(
+            string filePath,
+            ForegroundDispatcher foregroundDispatcher)
+        {
+            if (string.IsNullOrEmpty(filePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(filePath));
+            }
+
+            if (foregroundDispatcher == null)
+            {
+                throw new ArgumentNullException(nameof(foregroundDispatcher));
+            }
+
+            FilePath = filePath;
+            _normalizedFilePath = NormalizePath(FilePath);
+            _foregroundDispatcher = foregroundDispatcher;
+        }
+
+        public override string FilePath { get; }
+
+        public override void StartListening()
+        {
+            _foregroundDispatcher.AssertForegroundThread();
+
+            if (_listening)
+            {
+                return;
+            }
+
+            AttachToFileServiceEvents();
+
+            _listening = true;
+        }
+
+        public override void StopListening()
+        {
+            _foregroundDispatcher.AssertForegroundThread();
+
+            if (!_listening)
+            {
+                return;
+            }
+
+            DetachFromFileServiceEvents();
+
+            _listening = false;
+        }
+
+        // Virtual for testing
+        protected virtual void AttachToFileServiceEvents()
+        {
+            FileService.FileChanged += FileService_FileChanged;
+            FileService.FileCreated += FileService_FileCreated;
+            FileService.FileRemoved += FileService_FileRemoved;
+        }
+
+        // Virtual for testing
+        protected virtual void DetachFromFileServiceEvents()
+        {
+            FileService.FileChanged -= FileService_FileChanged;
+            FileService.FileCreated -= FileService_FileCreated;
+            FileService.FileRemoved -= FileService_FileRemoved;
+        }
+
+        private void FileService_FileChanged(object sender, FileEventArgs args) => HandleFileChangeEvent(FileChangeKind.Changed, args);
+
+        private void FileService_FileCreated(object sender, FileEventArgs args) => HandleFileChangeEvent(FileChangeKind.Added, args);
+
+        private void FileService_FileRemoved(object sender, FileEventArgs args) => HandleFileChangeEvent(FileChangeKind.Removed, args);
+
+        private void HandleFileChangeEvent(FileChangeKind changeKind, FileEventArgs args)
+        {
+            _foregroundDispatcher.AssertForegroundThread();
+
+            if (Changed == null)
+            {
+                return;
+            }
+
+            foreach (var fileEvent in args)
+            {
+                if (fileEvent.IsDirectory)
+                {
+                    continue;
+                }
+
+                var normalizedEventPath = NormalizePath(fileEvent.FileName.FullPath);
+                if (string.Equals(_normalizedFilePath, normalizedEventPath, StringComparison.OrdinalIgnoreCase))
+                {
+                    OnChanged(changeKind);
+                    return;
+                }
+            }
+        }
+
+        private void OnChanged(FileChangeKind changeKind)
+        {
+            _foregroundDispatcher.AssertForegroundThread();
+
+            var args = new FileChangeEventArgs(FilePath, changeKind);
+            Changed?.Invoke(this, args);
+        }
+
+        private static string NormalizePath(string path)
+        {
+            path = path.Replace('\\', '/');
+
+            return path;
+        }
+    }
+}

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/DefaultFileChangeTrackerFactory.cs

@@ -0,0 +1,35 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor
+{
+    internal class DefaultFileChangeTrackerFactory : FileChangeTrackerFactory
+    {
+        private readonly ForegroundDispatcher _foregroundDispatcher;
+
+        public DefaultFileChangeTrackerFactory(ForegroundDispatcher foregroundDispatcher)
+        {
+            if (foregroundDispatcher == null)
+            {
+                throw new ArgumentNullException(nameof(foregroundDispatcher));
+            }
+
+            _foregroundDispatcher = foregroundDispatcher;
+        }
+
+        public override FileChangeTracker Create(string filePath)
+        {
+            if (string.IsNullOrEmpty(filePath))
+            {
+                throw new ArgumentException(Resources.ArgumentCannotBeNullOrEmpty, nameof(filePath));
+            }
+
+            var fileChangeTracker = new DefaultFileChangeTracker(filePath, _foregroundDispatcher);
+            return fileChangeTracker;
+        }
+    }
+}

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/DefaultFileChangeTrackerFactoryFactory.cs

@@ -0,0 +1,29 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Composition;
+using Microsoft.CodeAnalysis.Host;
+using Microsoft.CodeAnalysis.Host.Mef;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor
+{
+    [Shared]
+    [ExportLanguageServiceFactory(typeof(FileChangeTrackerFactory), RazorLanguage.Name, ServiceLayer.Default)]
+    internal class DefaultFileChangeTrackerFactoryFactory : ILanguageServiceFactory
+    {
+        public ILanguageService CreateLanguageService(HostLanguageServices languageServices)
+        {
+            if (languageServices == null)
+            {
+                throw new ArgumentNullException(nameof(languageServices));
+            }
+
+            var foregroundDispatcher = languageServices.WorkspaceServices.GetRequiredService<ForegroundDispatcher>();
+            var errorReporter = languageServices.WorkspaceServices.GetRequiredService<ErrorReporter>();
+            return new DefaultFileChangeTrackerFactory(foregroundDispatcher);
+        }
+    }
+}

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/Properties/AssemblyInfo.cs

@@ -0,0 +1,7 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7")]

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/Properties/Resources.Designer.cs

@@ -10,6 +10,20 @@ namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor
         private static readonly ResourceManager _resourceManager
             = new ResourceManager("Microsoft.VisualStudio.Mac.LanguageServices.Razor.Resources", typeof(Resources).GetTypeInfo().Assembly);
 
+        /// <summary>
+        /// Value cannot be null or an empty string.
+        /// </summary>
+        internal static string ArgumentCannotBeNullOrEmpty
+        {
+            get => GetString("ArgumentCannotBeNullOrEmpty");
+        }
+
+        /// <summary>
+        /// Value cannot be null or an empty string.
+        /// </summary>
+        internal static string FormatArgumentCannotBeNullOrEmpty()
+            => GetString("ArgumentCannotBeNullOrEmpty");
+
         /// <summary>
         /// Razor Language Service error encountered.
         /// </summary>

src/Microsoft.VisualStudio.Mac.LanguageServices.Razor/Resources.resx

@@ -117,6 +117,9 @@
   <resheader name="writer">
     <value>System.Resources.ResXResourceWriter, System.Windows.Forms, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089</value>
   </resheader>
+  <data name="ArgumentCannotBeNullOrEmpty" xml:space="preserve">
+    <value>Value cannot be null or an empty string.</value>
+  </data>
   <data name="RazorLanguageServiceGeneralError" xml:space="preserve">
     <value>Razor Language Service error encountered.</value>
   </data>

test/Microsoft.VisualStudio.Editor.Razor.Test.Common/Properties/AssemblyInfo.cs

@@ -5,4 +5,5 @@ using System.Runtime.CompilerServices;
 [assembly: InternalsVisibleTo("Microsoft.CodeAnalysis.Razor.Workspaces.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.Editor.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("Microsoft.VisualStudio.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
+[assembly: InternalsVisibleTo("Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test, PublicKey=0024000004800000940000000602000000240000525341310004000001000100f33a29044fa9d740c9b3213a93e57c84b472c84e0b8a0e1ae48e67a9f8f6de9d5f7f3d52ac23e48ac51801f1dc950abe901da34d2a9e3baadb141a17c77ef3c565dd5ee5054b91cf63bb3c6ab83f72ab3aafe93d0fc3c2348b764fafb0b1c0733de51459aeab46580384bf9d74c4e28164b7cde247f891ba07891c9d872ad2bb")]
 [assembly: InternalsVisibleTo("DynamicProxyGenAssembly2, PublicKey=0024000004800000940000000602000000240000525341310004000001000100c547cac37abd99c8db225ef2f6c8a3602f3b3606cc9891605d02baa56104f4cfc0734aa39b93bf7852f7d9266654753cc297e7d2edfe0bac1cdcf9f717241550e0a7b191195b7667bb4f64bcb8e2121380fd1d9d46ad2d92d2d15605093924cceaf74c4861eff62abf69b9291ed0a340e113be11e6a7d3113e92484cf7045cc7")]

test/Microsoft.VisualStudio.LanguageServices.Razor.Test/DefaultFileChangeTrackerTest.cs

@@ -79,7 +79,7 @@ namespace Microsoft.VisualStudio.LanguageServices.Razor
         }
 
         [ForegroundFact]
-        public void StartListening_NotListening_DoesNothing()
+        public void StopListening_NotListening_DoesNothing()
         {
             // Arrange
             uint cookie = VSConstants.VSCOOKIE_NIL;

test/Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test/DefaultFileChangeTrackerTest.cs

@@ -0,0 +1,89 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.CodeAnalysis.Razor;
+using Microsoft.VisualStudio.Editor.Razor;
+using MonoDevelop.Core;
+using Moq;
+using Xunit;
+
+namespace Microsoft.VisualStudio.Mac.LanguageServices.Razor
+{
+    public class DefaultFileChangeTrackerTest : ForegroundDispatcherTestBase
+    {
+        [ForegroundFact]
+        public void StartListening_AdvisesForFileChange()
+        {
+            // Arrange
+            var tracker = new TestFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher);
+
+            // Act
+            tracker.StartListening();
+
+            // Assert
+            Assert.Equal(1, tracker.AttachToFileServiceEventsCount);
+        }
+
+        [ForegroundFact]
+        public void StartListening_AlreadyListening_DoesNothing()
+        {
+            // Arrange
+            var tracker = new TestFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher);
+            tracker.StartListening();
+
+            // Act
+            tracker.StartListening();
+
+            // Assert
+            Assert.Equal(1, tracker.AttachToFileServiceEventsCount);
+        }
+
+        [ForegroundFact]
+        public void StopListening_UnadvisesForFileChange()
+        {
+            // Arrange
+            var tracker = new TestFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher);
+            tracker.StartListening(); // Start listening for changes.
+
+            // Act
+            tracker.StopListening();
+
+            // Assert
+            Assert.Equal(1, tracker.AttachToFileServiceEventsCount);
+            Assert.Equal(1, tracker.DetachFromFileServiceEventsCount);
+        }
+
+        [ForegroundFact]
+        public void StopListening_NotListening_DoesNothing()
+        {
+            // Arrange
+            var tracker = new TestFileChangeTracker("C:/_ViewImports.cshtml", Dispatcher);
+
+            // Act
+            tracker.StopListening();
+
+            // Assert
+
+            Assert.Equal(0, tracker.AttachToFileServiceEventsCount);
+            Assert.Equal(0, tracker.DetachFromFileServiceEventsCount);
+        }
+
+        private class TestFileChangeTracker : DefaultFileChangeTracker
+        {
+            public TestFileChangeTracker(
+                string filePath, 
+                ForegroundDispatcher foregroundDispatcher) : base(filePath, foregroundDispatcher)
+            {
+            }
+
+            public int AttachToFileServiceEventsCount { get; private set; }
+
+            public int DetachFromFileServiceEventsCount { get; private set; }
+
+            protected override void AttachToFileServiceEvents() => AttachToFileServiceEventsCount++;
+
+            protected override void DetachFromFileServiceEvents() => DetachFromFileServiceEventsCount++;
+        }
+    }
+}

test/Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test/Microsoft.VisualStudio.Mac.LanguageServices.Razor.Test.csproj

@@ -0,0 +1,20 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <TargetFramework>net461</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <ProjectReference Include="..\..\src\Microsoft.VisualStudio.Mac.LanguageServices.Razor\Microsoft.VisualStudio.Mac.LanguageServices.Razor.csproj" />
+    <ProjectReference Include="..\Microsoft.VisualStudio.Editor.Razor.Test.Common\Microsoft.VisualStudio.Editor.Razor.Test.Common.csproj" />
+  </ItemGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Moq" Version="$(MoqPackageVersion)" />
+    <PackageReference Include="Newtonsoft.Json" Version="$(NewtonsoftJsonPackageVersion)" />
+    <PackageReference Include="xunit.analyzers" Version="$(XunitAnalyzersPackageVersion)" />
+    <PackageReference Include="xunit.runner.visualstudio" Version="$(XunitRunnerVisualStudioPackageVersion)" />
+    <PackageReference Include="xunit" Version="$(XunitPackageVersion)" />
+  </ItemGroup>
+
+</Project>