c# - 模拟 Entity Framework 长 LINQ 查询

Question

有一个 LINQ 查询表达式(如下)想要测试模拟 Entity Framework 。为了模拟我正在使用代码:Entity Framework Testing with a Mocking Framework这适用于其他查询但不适用于此

var query = from vwPs in _reportingDbContext.VwAccountNumber
join ps in _reportingDbContext.PaymentSummary
  on new
  {
      Key1 = vwPs.Id,
      Key2 = vwPs.AccountNumber,
      Key3 = true,
      Key4 = true
  }
     equals
     new
     {
         Key1 = ps.Id,
         Key2 = ps.AccountNumber,
         Key3 = ps.PaymentDate >= fromDateTime,
         Key4 = ps.PaymentDate < toDateTime
     }
     into viewJoinPayment
from ps in viewJoinPayment.DefaultIfEmpty()
join prg in generatedReportIds
     on ps.PaymentRef equals prg
     into paymentJoinGenerated
from prgRow in paymentJoinGenerated.DefaultIfEmpty()
where vwPs.Id == Id
select new
{
    vwPs.AccountNumber,
    Payments = ps,
    ReportGenerated = prgRow
};

在代码中此时执行查询'_inner'中的值

internal class TestDbAsyncEnumerator<T> : IDbAsyncEnumerator<T> {
    //...
    public Task<bool> MoveNextAsync(CancellationToken cancellationToken) 
    { 
        return Task.FromResult(_inner.MoveNext()); 
    }
    //...

? _inner {System.Linq.Enumerable.WhereSelectEnumerableIterator<<>f__AnonymousType11<<>f__AnonymousType10<<>f__AnonymousType9<<>f__AnonymousType7>, LL.Core.DataAccess.Models.PaymentSummaryEntity>, System.Collections.Generic.IEnumerable>, int>, <>f__AnonymousType12>} Current: null
Results View: Expanding the Results View will enumerate the IEnumerable

当它执行 MoveNext() 时获取异常

? _inner.MoveNext() '_inner.MoveNext()' threw an exception of type 'System.NullReferenceException' Data: {System.Collections.ListDictionaryInternal} HResult: -2147467261 HelpLink: null InnerException: null Message: "Object reference not set to an instance of an object." Source: "Anonymously Hosted DynamicMethods Assembly" StackTrace: " at lambda_method(Closure , <>f__AnonymousType92 )\r\n at
System.Linq.Enumerable.<GroupJoinIterator>d__404.MoveNext()\r\n at System.Linq.Enumerable.d__223.MoveNext()\r\n at
System.Linq.Enumerable.WhereSelectEnumerableIterator2.MoveNext()" TargetSite: {Int32 lambda_method(System.Runtime.CompilerServices.Closure, <>f__AnonymousType92[<>f__AnonymousType72[LL.Core.DataAccess.Models.VwAccountNumberEnt ity,System.Collections.Generic.IEnumerable`1[LL.Core.DataAccess.Models.PaymentSummaryEntity]],LL.Core.DataAccess.Models.PaymentSummaryEntity])}

尝试了一些更改，包括此处建议的更改 DbSet mock, no results while calling ToList secondly

还是遇到同样的问题。拜托，任何人都可以给一些光吗？

使用集成测试验证查询实现不是一种选择，因为老板希望像所有其他查询一样在单元测试级别对其进行测试。

更新:谢谢@Eduard Malakhov，这是尝试过的东西。如果同时删除“DefaultIfEmpty”并运行查询，它不会抛出异常。但是如何避免 DefaultIfEmpty 的异常呢？我如何修改模拟代码来检查这种情况，因为非模拟调用不会发生异常？

var query = from vwPs in _charityReportingDbContext.VwCharityAccountNumber
join ps in _charityReportingDbContext.PaymentSummary
  on new
  {
      Key1 = vwPs.CharityId,
      Key2 = vwPs.AccountNumber,
      Key3 = true,
      Key4 = true
  }
     equals
     new
     {
         Key1 = ps.CharityId,
         Key2 = ps.AccountNumber,
         Key3 = ps.PaymentDate >= fromDateTime,
         Key4 = ps.PaymentDate < toDateTime
     }
     into viewJoinPayment
select new
{
    vwPs.AccountNumber,
};

Answer 1

我的 hacky“解决方案”(是星期五，想回家 :)。删除异常但不幸的是，没有给出正确的结果。

public Task<bool> MoveNextAsync(CancellationToken cancellationToken){ 
try
{
    return Task.FromResult(_inner.MoveNext());
}
catch (Exception ex)
{
    return Task.FromResult(false);
}}