Xunit Assert中的异步lambda表达式.Throws

Question

我有一些测试代码断言重复Users无法通过我创建UserRepository.

User.cs:

public class User
{
    public int Id { get; set; }

    public string AccountAlias { get; set; }

    public string DisplayName { get; set; }

    public string Email { get; set; }

    public bool IsActive { get; set; }
}

UserRepository.cs:

public class UserRepository
{
    public virtual async Task<User> CreateAsync(User entity)
    {
        if (entity == null)
        {
            throw new ArgumentNullException("entity");
        }

        if (await GetDuplicateAsync(entity) != null)
        {
            throw new InvalidOperationException("This user already exists");
        }

        return Create(entity);
    }

    public async Task<User> GetDuplicateAsync(User user)
    {
        if (user == null)
        {
            throw new ArgumentNullException("user");
        }

        return await (from u in Users
                      where u.AccountAlias == user.AccountAlias && 
                            u.Id != user.Id && 
                            u.IsActive
                      select u).FirstOrDefaultAsync();
    }
}

UserRepositoryTests.cs:

public sealed class UserRepositoryTests : IDisposable
{
    public UserRepositoryTests()
    {
        UserRepository = new UserRepository(new FooEntities()); // DbContext 
                                                                // from EF
    }

    private UserRepository UserRepository { get; set; }

    [Fact]
    public void DuplicateUserCannotBeCreated()
    {
        var testUser = new User    // This test user already exists in database
        {
            Id = 0,
            AccountAlias = "domain\\foo",
            DisplayName = "Foo",
            Email = "foo@bar.com",
            IsActive = true
        };
        Assert.Throws<InvalidOperationException>(async () => 
            await UserRepository.CreateAsync(testUser));
    }

    public void Dispose()
    {
        if (UserRepository != null)
        {
            UserRepository.Dispose();
        }
    }
}

当我运行这个单元测试,Xunit.Sdk.ThrowsException被抛出(即我InvalidOperationException是不是抛出):

Assert.Throws()预期失败:System.InvalidOperationException实际:(没有抛出异常)

从调试器GetDuplicateAsync()进行了评估,但是当执行LINQ查询时,结果从未返回,因此没有抛出异常.有人可以帮忙吗？

Answer 1

xUnit Assert.Throws(至少在版本1.9.2上)不是异步感知的.这已在版本2中修复,现在有一个Assert.ThrowsAsync方法.

因此,您可以升级到xUnit 2或创建自己的方法以使其正常工作:

public async static Task<T> ThrowsAsync<T>(Func<Task> testCode) where T : Exception
{
    try
    {
        await testCode();
        Assert.Throws<T>(() => { }); // Use xUnit's default behavior.
    }
    catch (T exception)
    {
        return exception;
    }
    return null;
}

await ThrowsAsync<InvalidOperationException>(async () => await UserRepository.CreateAsync(testUser));

来自Haacked的要点.