static async void RebuildTests ()
		{
			throttling.Cancel ();
			throttling = new CancellationTokenSource ();
			try {
				await Task.Delay (ThrottlingTimeout, throttling.Token);
				if (throttling.Token.IsCancellationRequested)
					return;

				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);
			}
		}