如何在SpecFlowMS-Test中的后台线程上运行Entity Framework

如何解决如何在SpecFlowMS-Test中的后台线程上运行Entity Framework

我正在SpecFlow中运行集成测试。

测试涉及使用Entity Framework 6访问数据库。数据访问必须在后台线程上运行，因为代码涉及线程锁定逻辑我目前无法更改。

如果直接从测试线程启动EF查询，它将运行良好，但是不幸的是，在实际情况下，我必须从辅助线程执行。

示例被最小化为可能的最小样本，从而重现了错误：实际上，不仅有EF查询，而且它是第一个引发的查询。

我的测试代码如下：

    [When("...")]
    public async Task When_IReadData()
    {
        var context = new MyContext();

        // This works fine,but...
        var data1 = context.Whatevers.ToList();

        // Act
        var task = Task.Run(() =>
        {
            // ...in the real case I have to run it from a background thread.
            var data2 = context.Whatevers.ToList(); // This throws an exception
        });

        await task;
    }

一旦我尝试从中查询数据库，它就会遇到TimeoutException。

在创建上下文或显式使用线程而不是Task.Run的位置上，这没有区别。

这仅在“何时/然后绑定”中发生...将相同的代码放在其他地方（例如在Test Initialize中）可以正常工作。因此，我猜想有一些specFlow执行处理可以阻止查询完成。

这是一个例外：

Message: 
Test method Euv.Modules.DatenPflegen.Tests.V2.Features.StuecklistePflegen.KomponenteAusbauenFeature.VorDemAusbauenEinerKomponenteDieNichtINTIstKannAbgebrochenWerden_ threw exception: 
System.Data.Entity.Core.EntityCommandExecutionException: An error occurred while executing the command definition. See the inner exception for details. ---> System.Data.SqlClient.SqlException: Execution Timeout Expired.  The timeout period elapsed prior to completion of the operation or the server is not responding. ---> System.ComponentModel.Win32Exception: The wait operation timed out
Stack Trace: 
SqlConnection.OnError(SqlException exception,Boolean breakConnection,Action`1 wrapCloseInAction)
SqlInternalConnection.OnError(SqlException exception,Action`1 wrapCloseInAction)
TdsParser.ThrowExceptionAndWarning(TdsParserStateObject stateObj,Boolean callerHasConnectionLock,Boolean asyncClose)
TdsParser.TryRun(RunBehavior runBehavior,SqlCommand cmdHandler,SqlDataReader dataStream,BulkCopySimpleResultSet bulkCopyHandler,TdsParserStateObject stateObj,Boolean& dataReady)
SqlDataReader.TryConsumeMetaData()
SqlDataReader.get_MetaData()
SqlCommand.FinishExecuteReader(SqlDataReader ds,RunBehavior runBehavior,String resetOptionsString,Boolean isInternal,Boolean forDescribeParameterEncryption,Boolean shouldCacheForAlwaysEncrypted)
SqlCommand.RunExecuteReaderTds(CommandBehavior cmdBehavior,Boolean returnStream,Boolean async,Int32 timeout,Task& task,Boolean asyncWrite,Boolean inRetry,SqlDataReader ds,Boolean describeParameterEncryptionRequest)
SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior,String method,TaskCompletionSource`1 completion,Boolean& usedCache,Boolean inRetry)
SqlCommand.RunExecuteReader(CommandBehavior cmdBehavior,String method)
SqlCommand.ExecuteReader(CommandBehavior behavior,String method)
SqlCommand.ExecuteDbDataReader(CommandBehavior behavior)
DbCommand.ExecuteReader(CommandBehavior behavior)
DbCommandDispatcher.<Reader>b__c(DbCommand t,DbCommandInterceptionContext`1 c)
InternalDispatcher`1.Dispatch[TTarget,TInterceptionContext,TResult](TTarget target,Func`3 operation,TInterceptionContext interceptionContext,Action`3 executing,Action`3 executed)
DbCommandDispatcher.Reader(DbCommand command,DbCommandInterceptionContext interceptionContext)
InterceptableDbCommand.ExecuteDbDataReader(CommandBehavior behavior)
DbCommand.ExecuteReader(CommandBehavior behavior)
EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand,CommandBehavior behavior)
--- End of inner exception stack trace ---
EntityCommandDefinition.ExecuteStoreCommands(EntityCommand entityCommand,CommandBehavior behavior)
ObjectQueryExecutionPlan.Execute[TResultType](ObjectContext context,ObjectParameterCollection parameterValues)
<>c__DisplayClass7.<GetResults>b__6()
ObjectContext.ExecuteInTransaction[T](Func`1 func,IDbExecutionStrategy executionStrategy,Boolean startLocalTransaction,Boolean releaseConnectionOnSuccess)
<>c__DisplayClass7.<GetResults>b__5()
DefaultSqlExecutionStrategy.Execute[TResult](Func`1 operation)
ObjectQuery`1.GetResults(Nullable`1 forMergeOption)
IEnumerable<T>.GetEnumerator>b__0()
LazyEnumerator`1.MoveNext()
List`1.ctor(IEnumerable`1 collection)
Enumerable.ToList[TSource](IEnumerable`1 source)
StuecklistePflegenBinding.<When_IchBaueDieKomponenteAus>b__28_0() line 432
Task.InnerInvoke()
Task.Execute()
--- End of stack trace from previous location where exception was thrown ---
TaskAwaiter.ThrowForNonSuccess(Task task)
TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
TaskAwaiter.GetResult()
<When_IchBaueDieKomponenteAus>d__28.MoveNext() line 431
--- End of stack trace from previous location where exception was thrown ---
TaskAwaiter.ThrowForNonSuccess(Task task)
TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
<<InvokeBindingDelegateAsync>b__0>d.MoveNext() line 31
--- End of stack trace from previous location where exception was thrown ---
TaskAwaiter.ThrowForNonSuccess(Task task)
TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
<<RunSync>b__0>d.MoveNext()
--- End of stack trace from previous location where exception was thrown ---
ExclusiveSynchronizationContext.BeginMessageLoop() line 115
AsyncHelpers.RunSync[T](Func`1 task) line 71
SynchronousBindingDelegateInvoker.InvokeBindingDelegateAsync(Delegate bindingDelegate,Object[] invokeArgs) line 27
SynchronousBindingDelegateInvoker.InvokeDelegateSynchronously(Delegate bindingDelegate,Object[] invokeArgs) line 16
BindingInvoker.InvokeBinding(IBinding binding,IContextManager contextManager,Object[] arguments,ITestTracer testTracer,TimeSpan& duration) line 49
TestExecutionEngine.ExecuteStepMatch(BindingMatch match,Object[] arguments) line 521
TestExecutionEngine.ExecuteStep(IContextManager contextManager,StepInstance stepInstance) line 426
TestExecutionEngine.OnAfterLastStep() line 207
TestRunner.CollectScenarioErrors() line 59
KomponenteAusbauenFeature.ScenarioCleanup()
KomponenteAusbauenFeature.VorDemAusbauenEinerKomponenteDieNichtINTIstKannAbgebrochenWerden_() line 29

（来自实际测试。） 我的猜测是我来自SpecFlow的 ExclusiveSynchronizationContext 导致了此问题。

TimeOutException可能是由于EntityFramework的命令超时（30秒）引起的。

解决方法

我猜（基于堆栈跟踪），EF实际上运行SQL命令并且被阻塞了。在运行测试时，请检查SQL Server Management Studio中的活动进程，看看是否有任何进程被另一个进程阻止。