aspnetcore/src/Shared/E2ETesting/WaitAssert.cs

// Copyright (c) .NET Foundation. All rights reserved.
// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.

using System;
using System.Collections;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Runtime.ExceptionServices;
using OpenQA.Selenium;
using OpenQA.Selenium.DevTools;
using OpenQA.Selenium.Interactions;
using OpenQA.Selenium.Support.UI;
using Xunit;

namespace Microsoft.AspNetCore.E2ETesting
{
    // XUnit assertions, but hooked into Selenium's polling mechanism

    public static class WaitAssert
    {
        private static bool TestRunFailed = false;
        public static TimeSpan DefaultTimeout = TimeSpan.FromSeconds(E2ETestOptions.Instance.DefaultWaitTimeoutInSeconds);
        public static TimeSpan FailureTimeout = TimeSpan.FromSeconds(E2ETestOptions.Instance.DefaultAfterFailureWaitTimeoutInSeconds);

        public static void Equal<T>(this IWebDriver driver, T expected, Func<T> actual)
            => WaitAssertCore(driver, () => Assert.Equal(expected, actual()));

        public static void NotEqual<T>(this IWebDriver driver, T expected, Func<T> actual)
            => WaitAssertCore(driver, () => Assert.NotEqual(expected, actual()));

        public static void True(this IWebDriver driver, Func<bool> actual)
            => WaitAssertCore(driver, () => Assert.True(actual()));

        public static void True(this IWebDriver driver, Func<bool> actual, TimeSpan timeout)
            => WaitAssertCore(driver, () => Assert.True(actual()), timeout);

        public static void False(this IWebDriver driver, Func<bool> actual)
            => WaitAssertCore(driver, () => Assert.False(actual()));

        public static void Contains(this IWebDriver driver, string expectedSubstring, Func<string> actualString)
            => WaitAssertCore(driver, () => Assert.Contains(expectedSubstring, actualString()));

        public static void Collection<T>(this IWebDriver driver, Func<IEnumerable<T>> actualValues, params Action<T>[] elementInspectors)
            => WaitAssertCore(driver, () => Assert.Collection(actualValues(), elementInspectors));

        public static void Empty(this IWebDriver driver, Func<IEnumerable> actualValues)
            => WaitAssertCore(driver, () => Assert.Empty(actualValues()));

        public static void Single(this IWebDriver driver, Func<IEnumerable> actualValues)
            => WaitAssertCore(driver, () => Assert.Single(actualValues()));

        public static IWebElement Exists(this IWebDriver driver, By finder)
            => Exists(driver, finder, default);

        public static TElement Exists<TElement>(this IWebDriver driver, Func<TElement> actual, TimeSpan timeout)
            => WaitAssertCore(driver, actual, timeout);

        public static void DoesNotExist(this IWebDriver driver, By finder, TimeSpan timeout = default)
            => WaitAssertCore(driver, () =>
            {
                var elements = driver.FindElements(finder);
                Assert.Empty(elements);
            }, timeout);

        public static IWebElement Exists(this IWebDriver driver, By finder, TimeSpan timeout)
            => WaitAssertCore(driver, () =>
            {
                var elements = driver.FindElements(finder);
                Assert.NotEmpty(elements);
                var result = elements[0];
                return result;
            }, timeout);

        public static void Click(this IWebDriver driver, By selector)
            => WaitAssertCore(driver, () =>
            {
                driver.FindElement(selector).Click();
            });

        private static void WaitAssertCore(IWebDriver driver, Action assertion, TimeSpan timeout = default)
        {
            WaitAssertCore<object>(driver, () => { assertion(); return null; }, timeout);
        }

        private static TResult WaitAssertCore<TResult>(IWebDriver driver, Func<TResult> assertion, TimeSpan timeout = default)
        {
            if (timeout == default)
            {
                timeout = !TestRunFailed ? DefaultTimeout : FailureTimeout;
            }

            Exception lastException = null;
            TResult result = default;
            try
            {
                new WebDriverWait(driver, timeout).Until(_ =>
                {
                    try
                    {
                        result = assertion();
                        return true;
                    }
                    catch (Exception e)
                    {
                        lastException = e;
                        return false;
                    }
                });
            }
            catch (WebDriverTimeoutException)
            {
                // At this point at least one test failed, so we mark the test as failed. Any assertions after this one
                // will fail faster. There's a small race condition here between checking the value for TestRunFailed
                // above and setting it here, but nothing bad can come out of it. Worst case scenario, one or more
                // tests running concurrently might use the DefaultTimeout in their current assertion, which is fine.
                TestRunFailed = true;

                var innerHtml = driver.FindElement(By.CssSelector(":first-child")).GetAttribute("innerHTML");

                var fileId = $"{Guid.NewGuid():N}.png";
                var screenShotPath = Path.Combine(Path.GetFullPath(E2ETestOptions.Instance.ScreenShotsPath), fileId);
                var errors = driver.GetBrowserLogs(LogLevel.All).Select(c => c.ToString()).ToList();

                TakeScreenShot(driver, screenShotPath);
                var exceptionInfo = lastException != null ? ExceptionDispatchInfo.Capture(lastException) :
                    CaptureException(() => assertion());

                throw new BrowserAssertFailedException(errors, exceptionInfo.SourceException, screenShotPath, innerHtml);
            }

            return result;
        }

        private static ExceptionDispatchInfo CaptureException(Action assertion)
        {
            try
            {
                assertion();
                throw new InvalidOperationException("The assertion succeeded after the timeout.");
            }
            catch (Exception ex)
            {
                return ExceptionDispatchInfo.Capture(ex);
            }
        }

        private static void TakeScreenShot(IWebDriver driver, string screenShotPath)
        {
            if (driver is ITakesScreenshot takesScreenshot && E2ETestOptions.Instance.ScreenShotsPath != null)
            {
                try
                {
                    Directory.CreateDirectory(E2ETestOptions.Instance.ScreenShotsPath);

                    var screenShot = takesScreenshot.GetScreenshot();
                    screenShot.SaveAsFile(screenShotPath);
                }
                catch (Exception ex)
                {
                    Console.WriteLine($"Failed to take a screenshot {ex.ToString()}");
                }
            }
        }
    }
}