public void UpdateGuestProjectManager_ProjectChanged_ConfigurationChange() { // Arrange var oldHandle = new ProjectSnapshotHandleProxy( new Uri("vsls:/path/project.csproj"), RazorConfiguration.Default, "project", projectWorkspaceState: null); var newConfiguration = RazorConfiguration.Create(RazorLanguageVersion.Version_1_0, "Custom-1.0", Enumerable.Empty <RazorExtension>()); var newHandle = new ProjectSnapshotHandleProxy( oldHandle.FilePath, newConfiguration, oldHandle.RootNamespace, oldHandle.ProjectWorkspaceState); var synchronizationService = new ProjectSnapshotSynchronizationService( JoinableTaskFactory, SessionContext, Mock.Of <IProjectSnapshotManagerProxy>(), ProjectSnapshotManager); var hostProject = new HostProject("/guest/path/project.csproj", RazorConfiguration.Default, "project"); ProjectSnapshotManager.ProjectAdded(hostProject); ProjectSnapshotManager.ProjectConfigurationChanged(hostProject); var args = new ProjectChangeEventProxyArgs(oldHandle, newHandle, ProjectProxyChangeKind.ProjectChanged); // Act synchronizationService.UpdateGuestProjectManager(args); // Assert var project = Assert.Single(ProjectSnapshotManager.Projects); Assert.Equal("/guest/path/project.csproj", project.FilePath); Assert.Same(newConfiguration, project.Configuration); Assert.Empty(project.TagHelpers); }