c# – 如何正确编写异步XUnit测试？

我正在使用异步xUnit测试,我注意到不一致的传递行为：

public async Task FetchData()
{
    //Arrange
    var result = await arrangedService.FetchDataAsync().ConfigureAwait(false);
    //Assert
}

我已经完成了此测试执行的调用堆栈,并验证了我的所有库代码都在每个任务之后调用.ConfigureAwait(false).但是,尽管如此,在执行全部运行时,此测试和其他测试将间歇性地失败,但是当我在调试器上完成时,会通过断言和手动检查.很明显,我没有正确地做某事.我已经尝试在测试本身中删除对ConfigureAwait(false)的调用,以防有特殊的xUnit同步上下文,但它没有改变任何东西.以一致的方式测试异步代码的最佳方法是什么？

编辑好的,这是我尝试创建一个运行的代码的超简化示例,以提供正在发生的事情的示例：

using Graph = Microsoft.Azure.ActiveDirectory.GraphClient;

public async Task FetchData()
{
    var adUsers = baseUsers //IEnumerable<Graph.User>
        .Cast<Graph.IUser>()
        .ToList();
    var nextPageUsers = Enumerable
        .Range(GoodIdMin,GoodIdMax)
        .Select(number => new Graph.User
        {
            Mail = (-number).ToString()
        })
        .Cast<Graph.IUser>()
        .ToList();

    var mockUserPages = new Mock<IPagedCollection<Graph.IUser>>();
    mockUserPages
        .Setup(pages => pages.MorePagesAvailable)
        .Returns(true);
    mockUserPages
        .Setup(pages => pages.CurrentPage)
        .Returns(new ReadOnlyCollection<Graph.IUser>(adUsers));
    mockUserPages
        .Setup(pages => pages.GetNextPageAsync())
        .ReturnsAsync(mockUserPages.Object)
        .Callback(() =>
        {
            mockUserPages
                .Setup(pages => pages.CurrentPage)
                .Returns(new ReadOnlyCollection<Graph.IUser>(nextPageUsers));
            mockUserPages
                .Setup(pages => pages.MorePagesAvailable)
                .Returns(false);
        });

    var mockUsers = new Mock<Graph.IUserCollection>();
    mockUsers
        .Setup(src => src.ExecuteAsync())
        .ReturnsAsync(mockUserPages.Object);

    var mockGraphClient = new Mock<Graph.IActiveDirectoryClient>();
    mockGraphClient
        .Setup(src => src.Users)
        .Returns(mockUsers.Object);

    var mockDbUsers = CreateBasicmockDbSet(baseUsers.Take(10)
        .Select(user => new User
        {
            Mail = user.Mail
        })
        .AsQueryable());
    var mockContext = new Mock<MyDbContext>();
    mockContext
        .Setup(context => context.Set<User>())
        .Returns(mockDbUsers.Object);

    var mockGraPHProvider = new Mock<IGraPHProvider>(); 
    mockGraPHProvider
        .Setup(src => src.GetClient()) //Creates an IActiveDirectoryClient
        .Returns(mockGraphClient.Object);

    var getter = new UserGetter(mockContext.Object,mockGraPHProvider.Object);

    var result = await getter.GetData().ConfigureAwait(false);

    Assert.True(result.Success); //Not the actual assert
}

这是在var result = … line上执行的代码：

public UserGetterResult GetData()
{
    var adUsers = await GetAdUsers().ConfigureAwait(false);
    var dbUsers = Context.Set<User>().ToList(); //This is the injected context from before
    return new UserGetterResult //Just a POCO
    {
        AdUsers = adUsers
            .Except(/*Expression that indicates whether
             or not this user is in the database*/)
            .ProjectTo<User>()
            .ToList(),DbUsers = dbUsers.ProjectTo<User>().ToList() //Automapper 6.1.1
    };
}

private async Task<List<User>> GetAdUsers()
{
    var userPages = await client //Injected IActiveDirectoryClient from before
        .Users
        .ExecuteAsync()
        .ConfigureAwait(false);
    var users = userPages.CurrentPage.ToList();
    while(userPages.MorePagesAvailable)
    {
        userPages = await userPages.GetNextPageAsync().ConfigureAwait(false);
        users.AddRange(userPages.CurrentPage);
    }
    return users;
}

代码的目的是获取AD中但不是数据库的用户列表以及数据库中的用户列表.

编辑编辑因为我忘了在原始更新中包含它,所以在调用`IUserCollection.ExecuteAsync()时都会发生错误.

解决方法

IUserCollection.ExecuteAsync()似乎是根据原始帖子中显示的内容正确配置的.

现在关注以下方法……

private async Task<List<User>> GetAdUsers() {
    var userPages = await client //Injected IActiveDirectoryClient from before
        .Users
        .ExecuteAsync()
        .ConfigureAwait(false);
    var users = userPages.CurrentPage.ToList();
    while(userPages.MorePagesAvailable) {
        userPages = await userPages.GetNextPageAsync().ConfigureAwait(false);
        users.AddRange(userPages.CurrentPage);
    }
    return users;
}

我关心如何在模拟中设置用户页面.鉴于GetAdUsers方法的流程,最好使用SetupSequence来模拟重复调用CurrentPage和MorePagesAvailable.

var mockUserPages = new Mock<IPagedCollection<Graph.IUser>>();
mockUserPages
    .SetupSequence(_ => _.MorePagesAvailable)
    .Returns(true) // First time called to enter while loop
    .Returns(false); // Second time called to exit while loop
mockUserPages
    .SetupSequence(_ => _.CurrentPage)
    .Returns(new ReadOnlyCollection<Graph.IUser>(adUsers)) // First time called to get List
    .Returns(new ReadOnlyCollection<Graph.IUser>(nextPageUsers)); // Second time called to get next page
mockUserPages
    .Setup(pages => pages.GetNextPageAsync())
    .ReturnsAsync(mockUserPages.Object); // No need for callback

参考Moq Quickstart