static void RebuildTests ()
		{
			throttling.Cancel ();
			throttling = new CancellationTokenSource ();
			Task.Delay (ThrottlingTimeout, throttling.Token).ContinueWith (async (task) => {
				if (task.IsCanceled)
					return;
				try {
					if (rootTests != null) {
						foreach (IDisposable t in rootTests)
							t.Dispose ();
					}
					List<UnitTest> list = new List<UnitTest> ();
					rebuildTestsCts.Cancel ();
					rebuildTestsCts = new CancellationTokenSource ();
					var token = rebuildTestsCts.Token;
					var items = IdeApp.Workspace.Items.ToArray ();
					await Task.Run (() => {
						foreach (WorkspaceItem it in items) {
							if (token.IsCancellationRequested)
								return;
							UnitTest t = BuildTest (it);
							if (t != null)
								list.Add (t);
						}
					}, token);
					if (token.IsCancellationRequested)
						return;
					rootTests = list.ToArray ();
					NotifyTestSuiteChanged ();
				} catch (OperationCanceledException) {
				} catch (Exception ex) {
					LoggingService.LogError ("Exception gathering unit tests.", ex);
				}
			}, throttling.Token, TaskContinuationOptions.None, Runtime.MainTaskScheduler);
		}