public void SingleTask_AfterLongDelay_AllowsIdleNavigation()
        {
            var    browser  = new BrowserStub();
            string target   = "http://any old web address";
            var    isolator = new NavigationIsolator();

            isolator.Navigate(browser, target);
            Assert.That(browser.NavigateTarget, Is.EqualTo(target));

            string target2 = "http://some other web address";
            var    start   = DateTime.Now;
            var    success = false;

            while (!success && DateTime.Now - start < new TimeSpan(0, 0, 0, 2, 300))
            {
                success = isolator.NavigateIfIdle(browser, target2);
                Application.DoEvents();                 // allow timer to tick.
            }
            Assert.That(() => browser.NavigateTarget, Is.EqualTo(target2), "Idle navigation should have proceeded eventually");
            Assert.That(success, "NavigateIfIdle should eventually succeed");

            browser.NormalTermination();             // possibly the long-delayed notification of the first nav, but more likely the idle navigation.
            Assert.That(browser.EventHandlerCount, Is.EqualTo(0), "event handlers should be removed once last navigation completed");
        }