如何使用Entity Framework Core模拟异步存储库

Z时代
2024-01-10
分类：问答

我正在尝试为调用异步存储库的类创建一个单元测试。我正在使用ASP.NET Core和Entity Framework Core。我的通用存储库如下所示。

public class EntityRepository<TEntity> : IEntityRepository<TEntity> where TEntity : class
{
    private readonly SaasDispatcherDbContext _dbContext;
    private readonly DbSet<TEntity> _dbSet;
    public EntityRepository(SaasDispatcherDbContext dbContext)
    {
        _dbContext = dbContext;
        _dbSet = dbContext.Set<TEntity>();
    }
    public virtual IQueryable<TEntity> GetAll()
    {
        return _dbSet;
    }
    public virtual async Task<TEntity> FindByIdAsync(int id)
    {
        return await _dbSet.FindAsync(id);
    }
    public virtual IQueryable<TEntity> FindBy(Expression<Func<TEntity, bool>> predicate)
    {
        return _dbSet.Where(predicate);
    }
    public virtual void Add(TEntity entity)
    {
        _dbSet.Add(entity);
    }
    public virtual void Delete(TEntity entity)
    {
        _dbSet.Remove(entity);
    }
    public virtual void Update(TEntity entity)
    {
        _dbContext.Entry(entity).State = EntityState.Modified;
    }
    public virtual async Task SaveChangesAsync()
    {
        await _dbContext.SaveChangesAsync();
    }
}

然后，我有一个服务类，在存储库的一个实例上调用FindBy和FirstOrDefaultAsync：

    public async Task<Uri> GetCompanyProductURLAsync(Guid externalCompanyID, string productCode, Guid loginToken)
    {            
        CompanyProductUrl companyProductUrl = await _Repository.FindBy(u => u.Company.ExternalCompanyID == externalCompanyID && u.Product.Code == productCode.Trim()).FirstOrDefaultAsync();
        if (companyProductUrl == null)
        {
            return null;
        }
        var builder = new UriBuilder(companyProductUrl.Url);
        builder.Query = $"-s{loginToken.ToString()}";
        return builder.Uri;
    }

我正在尝试在下面的测试中模拟存储库调用：

    [Fact]
    public async Task GetCompanyProductURLAsync_ReturnsNullForInvalidCompanyProduct()
    {
        var companyProducts = Enumerable.Empty<CompanyProductUrl>().AsQueryable();
        var mockRepository = new Mock<IEntityRepository<CompanyProductUrl>>();
        mockRepository.Setup(r => r.FindBy(It.IsAny<Expression<Func<CompanyProductUrl, bool>>>())).Returns(companyProducts);
        var service = new CompanyProductService(mockRepository.Object);
        var result = await service.GetCompanyProductURLAsync(Guid.NewGuid(), "wot", Guid.NewGuid());
        Assert.Null(result);
    }

但是，当测试执行对存储库的调用时，出现以下错误：

The provider for the source IQueryable doesn't implement IAsyncQueryProvider. Only providers that implement IEntityQueryProvider can be used for Entity Framework asynchronous operations.

如何正确模拟存储库以使其正常工作？

回答：

感谢@Nkosi为我指向的链接提供了在EF 6中执行相同操作的示例：https ://msdn.microsoft.com/zh-cn/library/dn314429.aspx

。这与EF Core并不完全一样，但是我能够从它开始并进行修改以使其正常工作。下面是我创建的用于“模拟” IAsyncQueryProvider的测试类：

internal class TestAsyncQueryProvider<TEntity> : IAsyncQueryProvider
{
    private readonly IQueryProvider _inner;
    internal TestAsyncQueryProvider(IQueryProvider inner)
    {
        _inner = inner;
    }
    public IQueryable CreateQuery(Expression expression)
    {
        return new TestAsyncEnumerable<TEntity>(expression);
    }
    public IQueryable<TElement> CreateQuery<TElement>(Expression expression)
    {
        return new TestAsyncEnumerable<TElement>(expression);
    }
    public object Execute(Expression expression)
    {
        return _inner.Execute(expression);
    }
    public TResult Execute<TResult>(Expression expression)
    {
        return _inner.Execute<TResult>(expression);
    }
    public IAsyncEnumerable<TResult> ExecuteAsync<TResult>(Expression expression)
    {
        return new TestAsyncEnumerable<TResult>(expression);
    }
    public Task<TResult> ExecuteAsync<TResult>(Expression expression, CancellationToken cancellationToken)
    {
        return Task.FromResult(Execute<TResult>(expression));
    }
}
internal class TestAsyncEnumerable<T> : EnumerableQuery<T>, IAsyncEnumerable<T>, IQueryable<T>
{
    public TestAsyncEnumerable(IEnumerable<T> enumerable)
        : base(enumerable)
    { }
    public TestAsyncEnumerable(Expression expression)
        : base(expression)
    { }
    public IAsyncEnumerator<T> GetEnumerator()
    {
        return new TestAsyncEnumerator<T>(this.AsEnumerable().GetEnumerator());
    }
    IQueryProvider IQueryable.Provider
    {
        get { return new TestAsyncQueryProvider<T>(this); }
    }
}
internal class TestAsyncEnumerator<T> : IAsyncEnumerator<T>
{
    private readonly IEnumerator<T> _inner;
    public TestAsyncEnumerator(IEnumerator<T> inner)
    {
        _inner = inner;
    }
    public void Dispose()
    {
        _inner.Dispose();
    }
    public T Current
    {
        get
        {
            return _inner.Current;
        }
    }
    public Task<bool> MoveNext(CancellationToken cancellationToken)
    {
        return Task.FromResult(_inner.MoveNext());
    }
}

这是我使用这些类的更新的测试用例：

[Fact]
public async Task GetCompanyProductURLAsync_ReturnsNullForInvalidCompanyProduct()
{
    var companyProducts = Enumerable.Empty<CompanyProductUrl>().AsQueryable();
    var mockSet = new Mock<DbSet<CompanyProductUrl>>();
    mockSet.As<IAsyncEnumerable<CompanyProductUrl>>()
        .Setup(m => m.GetEnumerator())
        .Returns(new TestAsyncEnumerator<CompanyProductUrl>(companyProducts.GetEnumerator()));
    mockSet.As<IQueryable<CompanyProductUrl>>()
        .Setup(m => m.Provider)
        .Returns(new TestAsyncQueryProvider<CompanyProductUrl>(companyProducts.Provider));
    mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.Expression).Returns(companyProducts.Expression);
    mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.ElementType).Returns(companyProducts.ElementType);
    mockSet.As<IQueryable<CompanyProductUrl>>().Setup(m => m.GetEnumerator()).Returns(() => companyProducts.GetEnumerator());
    var contextOptions = new DbContextOptions<SaasDispatcherDbContext>();
    var mockContext = new Mock<SaasDispatcherDbContext>(contextOptions);
    mockContext.Setup(c => c.Set<CompanyProductUrl>()).Returns(mockSet.Object);
    var entityRepository = new EntityRepository<CompanyProductUrl>(mockContext.Object);
    var service = new CompanyProductService(entityRepository);
    var result = await service.GetCompanyProductURLAsync(Guid.NewGuid(), "wot", Guid.NewGuid());
    Assert.Null(result);
}