Added failing test for #1493.

Unfortunately it will only fail on some runs. Seems that if it gets past the first iteration, it will always pass...

Author: grokys

test/UnitTests/GitHub.TeamFoundation/VSGitExtTests.cs

@@ -9,6 +9,9 @@
 using NUnit.Framework;
 using NSubstitute;
 using Microsoft.VisualStudio.TeamFoundation.Git.Extensibility;
+using System.Threading.Tasks;
+using System.Linq;
+using GitHub.TeamFoundation.Services;
 
 public class VSGitExtTests
 {
@@ -171,9 +174,32 @@ public void ExceptionRefreshingRepositories_ReturnsEmptyList()
             repoFactory.Received(1).Create(repoPath);
             Assert.That(activeRepositories.Count, Is.EqualTo(0));
         }
+
+        [Test]
+        public async Task ThreadingStressTest()
+        {
+            for (var i = 0; i < 100; ++i)
+            {
+                var gitExt = new MockGitExt();
+                var repoFactory = new MockRepositoryFactory();
+                var target = CreateVSGitExt(gitExt: gitExt, repoFactory: repoFactory);
+                var activeRepositories1 = CreateActiveRepositories("repo1");
+                var activeRepositories2 = CreateActiveRepositories("repo2");
+                var task1 = Task.Run(() => gitExt.ActiveRepositories = activeRepositories1);
+                await Task.Delay(1);
+                var task2 = Task.Run(() => gitExt.ActiveRepositories = activeRepositories2);
+
+                await Task.WhenAll(task1, task2);
+
+                Assert.That(
+                    target.ActiveRepositories.Single().LocalPath,
+                    Is.EqualTo("repo2"),
+                    $"Failed at iteration {i}");
+            }
+        }
     }
 
-    static IReadOnlyList<IGitRepositoryInfo> CreateActiveRepositories(IList<string> repositoryPaths)
+    static IReadOnlyList<IGitRepositoryInfo> CreateActiveRepositories(params string[] repositoryPaths)
     {
         var repositories = new List<IGitRepositoryInfo>();
         foreach (var repositoryPath in repositoryPaths)
@@ -203,9 +229,8 @@ static VSGitExt CreateVSGitExt(IVSUIContext context = null, IGitExt gitExt = nul
         return vsGitExt;
     }
 
-    static IGitExt CreateGitExt(IList<string> repositoryPaths = null)
+    static IGitExt CreateGitExt(params string[] repositoryPaths)
     {
-        repositoryPaths = repositoryPaths ?? Array.Empty<string>();
         var gitExt = Substitute.For<IGitExt>();
         var repoList = CreateActiveRepositories(repositoryPaths);
         gitExt.ActiveRepositories.Returns(repoList);
@@ -218,4 +243,34 @@ static IVSUIContext CreateVSUIContext(bool isActive)
         context.IsActive.Returns(isActive);
         return context;
     }
+
+    class MockGitExt : IGitExt
+    {
+        IReadOnlyList<IGitRepositoryInfo> activeRepositories = new IGitRepositoryInfo[0];
+
+        public IReadOnlyList<IGitRepositoryInfo> ActiveRepositories
+        {
+            get { return activeRepositories; }
+            set
+            {
+                if (activeRepositories != value)
+                {
+                    activeRepositories = value;
+                    PropertyChanged?.Invoke(this, new PropertyChangedEventArgs(nameof(ActiveRepositories)));
+                }
+            }
+        }
+
+        public event PropertyChangedEventHandler PropertyChanged;
+    }
+
+    class MockRepositoryFactory : ILocalRepositoryModelFactory
+    {
+        public ILocalRepositoryModel Create(string localPath)
+        {
+            var result = Substitute.For<ILocalRepositoryModel>();
+            result.LocalPath.Returns(localPath);
+            return result;
+        }
+    }
 }