Add tests to check if SonarQubeNavigationItem is free-threaded (#4882)

Part of #4856

src/Integration.TeamExplorer.UnitTests/SonarQubeNavigationItemTests.cs

@@ -20,7 +20,9 @@
 
 using System;
 using FluentAssertions;
+using Microsoft.TeamFoundation.Controls;
 using Microsoft.VisualStudio.TestTools.UnitTesting;
+using Moq;
 using SonarLint.VisualStudio.Integration.Resources;
 using SonarLint.VisualStudio.Integration.TeamExplorer;
 using SonarLint.VisualStudio.TestInfrastructure;
@@ -30,29 +32,49 @@ namespace SonarLint.VisualStudio.Integration.UnitTests.TeamExplorer
     [TestClass]
     public class SonarQubeNavigationItemTests
     {
+        [TestMethod]
+        [Ignore] // Object is created successfully, but an exception when
+                 // the MEF composition contained is disposed causing the test to fail
+        public void MefCtor_CheckIsExported()
+                => MefTestHelpers.CheckTypeCanBeImported<SonarQubeNavigationItem, ITeamExplorerNavigationItem>(
+                    MefTestHelpers.CreateExport<ITeamExplorerController>());
+
+        [TestMethod]
+        public void CheckIsNonSharedMefComponent()
+            => MefTestHelpers.CheckIsNonSharedMefComponent<SonarQubeNavigationItem>();
+
+        [TestMethod]
+        public void MefCtor_DoesNotCallAnyServices()
+        {
+            var controller = new Mock<ITeamExplorerController>();
+
+            _ = new SonarQubeNavigationItem(controller.Object);
+
+            // The MEF constructor should be free-threaded, which it will be if
+            // it doesn't make any external calls.
+            controller.Invocations.Should().BeEmpty();
+        }
+
         [TestMethod]
         public void SonarQubeNavigationItem_Execute()
         {
             // Arrange
-            var controller = new ConfigurableTeamExplorerController();
+            var controller = new Mock<ITeamExplorerController>();
 
-            var testSubject = new SonarQubeNavigationItem(controller);
+            var testSubject = CreateTestSubject(controller.Object);
 
             // Act
             testSubject.Execute();
 
             // Assert
-            controller.ShowConnectionsPageCallsCount.Should().Be(1);
+            controller.Verify(x => x.ShowSonarQubePage(), Times.Once);
         }
 
         [TestMethod]
         public void SonarQubeNavigationItem_Ctor()
         {
-            // Arrange
-            var controller = new ConfigurableTeamExplorerController();
-
-            // Act
-            var testSubject = new SonarQubeNavigationItem(controller);
+            // Arrange & Act
+            var testSubject = CreateTestSubject();
 
             // Assert
             testSubject.IsVisible.Should().BeTrue("Nav item should be visible");
@@ -67,5 +89,8 @@ public void SonarQubeNavigationItem_Ctor_NullArgChecks()
         {
             Exceptions.Expect<ArgumentNullException>(() => new SonarQubeNavigationItem(null));
         }
+
+        private static SonarQubeNavigationItem CreateTestSubject(ITeamExplorerController controller = null)
+            => new SonarQubeNavigationItem(controller ?? Mock.Of<ITeamExplorerController>());
     }
 }

src/Integration.TeamExplorer/SonarQubeNavigationItem.cs

@@ -28,6 +28,7 @@
 namespace SonarLint.VisualStudio.Integration.TeamExplorer
 {
     [TeamExplorerNavigationItem(SonarQubeNavigationItem.ItemId, SonarQubeNavigationItem.Priority, TargetPageId = SonarQubePage.PageId)]
+    [PartCreationPolicy(CreationPolicy.NonShared)] // The VS navigations in MS.TeamFoundation.TeamExplorer.Navigation are non-shared
     internal class SonarQubeNavigationItem : TeamExplorerNavigationItemBase
     {
         public const string ItemId = "172AF455-5F42-46FC-BFE6-23227A05806B";
@@ -49,6 +50,12 @@ internal SonarQubeNavigationItem([Import] ITeamExplorerController controller)
             this.IsVisible = true;
             this.IsEnabled = true;
 
+            // Note on threading:
+            // MEF constructors must be free-threaded i.e. capable of running to completion the calling thread.
+            // There's no public documentation on how these whether it's ok to create WPF artefacts like brushes
+            // and icons in the constructor. However, this is what the VS Team Explorer implementations of this
+            // class are doing, so we assume it's ok.
+            // See [VS installation directory]\Common7\IDE\CommonExtensions\Microsoft\TeamFoundation\Team Explorer\Microsoft.TeamFoundation.TeamExplorer.Navigation.dll
             var image = ResourceHelper.Get<DrawingImage>("SonarQubeServerIcon");
             this.m_icon = image != null ? new DrawingBrush(image.Drawing) : null;