我开始在我的生产代码中使用 SQL Server 的 tSQLt 单元测试。目前，我使用Erland Sommarskog 的SQL Server 错误处理模式。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.SommarskogRollback') IS NOT NULL
DROP PROCEDURE dbo.SommarskogRollback;
GO
CREATE PROCEDURE dbo.SommarskogRollback
AS
BEGIN; /*Stored Procedure*/
SET XACT_ABORT, NOCOUNT ON;
BEGIN TRY;
BEGIN TRANSACTION;
RAISERROR('This is just a test. Had this been an actual error, we would have given you some cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH;
IF @@TRANCOUNT > 0
ROLLBACK TRANSACTION;
THROW;
END CATCH;
END; /*Stored Procedure*/
GO
Erland Sommarskog 建议我们始终SET XACT_ABORT ON，因为只有这样 SQL Server 才会以（大部分）一致的方式处理错误。
但是，这在使用 tSQLt 时会产生问题。tSQLt 在显式事务中执行所有测试。当测试完成时，整个事务回滚。这使得清理测试工件完全无痛。然而，在 XACT_ABORT ON 的情况下，任何在 TRY 块内抛出的错误都会立即导致该事务的失败。事务必须完全回滚。它不能提交，也不能回滚到保存点。事实上，在事务回滚之前，没有任何内容可以写入该会话内的事务日志。但是，tSQLt 无法正确跟踪测试结果，除非在测试结束时事务处于打开状态。tSQLt 停止执行并抛出 ROLLBACK ERROR for doomed交易。失败的测试显示错误状态（而不是成功或失败），后续测试不会运行。
tSQLt 的创建者 Sebastian Meine 推荐了一种不同的错误处理模式。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.MeineRollback') IS NOT NULL
DROP PROCEDURE dbo.MeineRollback;
GO
CREATE PROCEDURE dbo.MeineRollback
AS
BEGIN /*Stored Procedure*/
SET NOCOUNT ON;
/* We declare the error variables here, populate them inside the CATCH
* block and then do our error handling after exiting the CATCH block
*/
DECLARE @ErrorNumber INT
,@MessageTemplate NVARCHAR(4000)
,@ErrorMessage NVARCHAR(4000)
,@ErrorProcedure NVARCHAR(126)
,@ErrorLine INT
,@ErrorSeverity INT
,@ErrorState INT
,@RaisErrorState INT
,@ErrorLineFeed NCHAR(1) = CHAR(10)
,@ErrorStatus INT = 0
,@SavepointName VARCHAR(32) = REPLACE( (CAST(NEWID() AS VARCHAR(36))), '-', '');
/*Savepoint names are 32 characters and must be unique. UNIQUEIDs are 36, four of which are dashes.*/
BEGIN TRANSACTION; /*If a transaction is already in progress, this just increments the transaction count*/
SAVE TRANSACTION @SavepointName;
BEGIN TRY;
RAISERROR('This is a test. Had this been an actual error, Sebastian would have given you a meaningful error message.', 16, 1);
END TRY
BEGIN CATCH;
/* Build a message string with placeholders for the original error information
* Note: "%d" & "%s" are placeholders (substitution parameters) which capture
* the values from the argument list of the original error message.
*/
SET @MessageTemplate = N': Error %d, Severity %d, State %d, ' + @ErrorLineFeed
+ N'Procedure %s, Line %d, ' + @ErrorLineFeed
+ N', Message: %s';
SELECT @ErrorStatus = 1
,@ErrorMessage = ERROR_MESSAGE()
,@ErrorNumber = ERROR_NUMBER()
,@ErrorProcedure = ISNULL(ERROR_PROCEDURE(), '-')
,@ErrorLine = ERROR_LINE()
,@ErrorSeverity = ERROR_SEVERITY()
,@ErrorState = ERROR_STATE()
,@RaisErrorState = CASE ERROR_STATE()
WHEN 0 /*RAISERROR Can't generate errors with State = 0*/
THEN 1
ELSE ERROR_STATE()
END;
END CATCH;
/*Rollback to savepoint if error occurred. This does not affect the transaction count.*/
IF @ErrorStatus <> 0
ROLLBACK TRANSACTION @SavepointName;
/*If this procedure executed inside a transaction, then the commit just subtracts one from the transaction count.*/
COMMIT TRANSACTION;
IF @ErrorStatus = 0
RETURN 0;
ELSE
BEGIN; /*Re-throw error*/
/*Rethrow the error. The msg_str parameter will contain the original error information*/
RAISERROR( @MessageTemplate /*msg_str parameter as message format template*/
,@ErrorSeverity /*severity parameter*/
,@RaisErrorState /*state parameter*/
,@ErrorNumber /*argument: original error number*/
,@ErrorSeverity /*argument: original error severity*/
,@ErrorState /*argument: original error state*/
,@ErrorProcedure /*argument: original error procedure name*/
,@ErrorLine /*argument: original error line number*/
,@ErrorMessage /*argument: original error message*/
);
RETURN -1;
END; /*Re-throw error*/
END /*Stored Procedure*/
GO
他声明错误变量，开始事务，设置保存点，然后在 TRY 块内执行过程代码。如果 TRY 块抛出错误，则执行传递到 CATCH 块，该块填充错误变量。然后执行超出 TRY CATCH 块。出错时，事务将回滚到过程开始时设置的保存点。然后事务提交。由于 SQL Server 处理嵌套事务的方式，当在另一个事务中执行时，此 COMMIT 只是从事务计数器中减去一个。（嵌套事务在 SQL Server 中确实不存在。）
塞巴斯蒂安创造了一个非常整洁的图案。执行链中的每个过程都会清理自己的事务。不幸的是，这种模式有一个大问题： 注定的交易。注定的事务打破了这种模式，因为它们无法回滚到保存点或提交。他们只能完全回滚。当然，这意味着您不能在使用 TRY-CATCH 块时将 XACT_ABORT 设置为 ON（并且您应该始终使用 TRY-CATCH 块。）即使 XACT_ABORT 为 OFF，许多错误（例如编译错误）无论如何都会导致事务失败. 此外，保存点不适用于分布式事务。
我该如何解决这个问题？我需要一个可以在 tSQLt 测试框架中工作的错误处理模式，并且还可以在生产环境中提供一致、正确的错误处理。我可以在运行时检查环境并相应地调整行为。（请参见下面的示例。）但是，我不喜欢这样。这对我来说就像一个黑客。它要求开发环境配置一致。更糟糕的是，我不测试我的实际生产代码。有没有人有一个绝妙的解决方案？
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.ModifiedRollback') IS NOT NULL
DROP PROCEDURE dbo.ModifiedRollback;
GO
CREATE PROCEDURE dbo.ModifiedRollback
AS
BEGIN; /*Stored Procedure*/
SET NOCOUNT ON;
IF RIGHT(@@SERVERNAME, 9) = '\LOCALDEV'
SET XACT_ABORT OFF;
ELSE
SET XACT_ABORT ON;
BEGIN TRY;
BEGIN TRANSACTION;
RAISERROR('This is just a test. Had this been an actual error, we would have given you some cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
END TRY
BEGIN CATCH;
IF @@TRANCOUNT > 0 AND RIGHT(@@SERVERNAME,9) <> '\LOCALDEV'
ROLLBACK TRANSACTION;
THROW;
END CATCH;
END; /*Stored Procedure*/
GO
编辑：经过进一步测试，我发现我修改后的回滚也不起作用。当过程抛出错误时，它退出而不回滚或提交。tSQLt 引发错误，因为过程退出时的@@TRANCOUNT 与过程启动时的计数不匹配。经过反复试验，我找到了一种适用于我的测试的解决方法。它结合了两种错误处理方法 - 使错误处理更加复杂，并且某些代码路径无法测试。我很想找到更好的解决方案。
USE TempDB;
SET ANSI_NULLS, QUOTED_IDENTIFIER ON;
GO
IF OBJECT_ID('dbo.TestedRollback') IS NOT NULL
DROP PROCEDURE dbo.TestedRollback;
GO
CREATE PROCEDURE dbo.TestedRollback
AS
BEGIN /*Stored Procedure*/
SET NOCOUNT ON;
/* Due to the way tSQLt uses transactions and the way SQL Server handles errors, we declare our error-handling
* variables here, populate them inside the CATCH block and then do our error-handling after exiting
*/
DECLARE @ErrorStatus BIT
,@ErrorNumber INT
,@MessageTemplate NVARCHAR(4000)
,@ErrorMessage NVARCHAR(4000)
,@ErrorProcedure NVARCHAR(126)
,@ErrorLine INT
,@ErrorSeverity INT
,@ErrorState INT
,@RaisErrorState INT
,@ErrorLineFeed NCHAR(1) = CHAR(10)
,@FALSE BIT = CAST(0 AS BIT)
,@TRUE BIT = CAST(1 AS BIT)
,@tSQLtEnvironment BIT
,@SavepointName VARCHAR(32) = REPLACE( (CAST(NEWID() AS VARCHAR(36))), '-', '');
/*Savepoint names are 32 characters long and must be unique. UNIQUEIDs are 36, four of which are dashes*/
/* The tSQLt Unit Testing Framework we use in our local development environments must maintain open transactions during testing. So,
* we don't roll back transactions during testing. Also, doomed transactions can't stay open, so we SET XACT_ABORT OFF while testing.
*/
IF RIGHT(@@SERVERNAME, 9) = '\LOCALDEV'
SET @tSQLtEnvironment = @TRUE
ELSE
SET @tSQLtEnvironment = @FALSE;
IF @tSQLtEnvironment = @TRUE
SET XACT_ABORT OFF;
ELSE
SET XACT_ABORT ON;
BEGIN TRY;
SET ROWCOUNT 0; /*The ROWCOUNT setting can be updated outside the procedure and changes its behavior. This sets it to the default.*/
SET @ErrorStatus = @FALSE;
BEGIN TRANSACTION;
/*We need a save point to roll back to in the tSQLt Environment.*/
IF @tSQLtEnvironment = @TRUE
SAVE TRANSACTION @SavepointName;
RAISERROR('Cryptic gobbledygook.', 16, 1);
COMMIT TRANSACTION;
RETURN 0;
END TRY
BEGIN CATCH;
SET @ErrorStatus = @TRUE;
/* Build a message string with placeholders for the original error information
* Note: "%d" & "%s" are placeholders (substitution parameters) which capture
* the values from the argument list of the original error message.
*/
SET @MessageTemplate = N': Error %d, Severity %d, State %d, ' + @ErrorLineFeed
+ N'Procedure %s, Line %d, ' + @ErrorLineFeed
+ N', Message: %s';
SELECT @ErrorMessage = ERROR_MESSAGE()
,@ErrorNumber = ERROR_NUMBER()
,@ErrorProcedure = ISNULL(ERROR_PROCEDURE(), '-')
,@ErrorLine = ERROR_LINE()
,@ErrorSeverity = ERROR_SEVERITY()
,@ErrorState = ERROR_STATE()
,@RaisErrorState = CASE ERROR_STATE()
WHEN 0 /*RAISERROR Can't generate errors with State = 0*/
THEN 1
ELSE ERROR_STATE()
END;
END CATCH;
/* Due to the way the tSQLt test framework uses transactions, we use two different error-handling schemes:
* one for unit-testing and the other for our main Test/Staging/Production environments. In those environments
* we roll back transactions in the CATCH block in the event of an error. In unit-testing, on the other hand,
* we begin a transaction and set a save point. If an error occurs we roll back to the save point and then
* commit the transaction. Since tSQLt executes all test in a single explicit transaction, starting a
* transaction at the beginning of this stored procedure just adds one to @@TRANCOUNT. Committing the
* transaction subtracts one from @@TRANCOUNT. Rolling back to a save point does not affect @@TRANCOUNT.
*/
IF @ErrorStatus = @TRUE
BEGIN; /*Error Handling*/
IF @tSQLtEnvironment = @TRUE
BEGIN; /*tSQLt Error Handling*/
ROLLBACK TRANSACTION @SavepointName; /*Rolls back to save point but does not affect @@TRANCOUNT*/
COMMIT TRANSACTION; /*Subtracts one from @@TRANCOUNT*/
END; /*tSQLt Error Handling*/
ELSE IF @@TRANCOUNT > 0
ROLLBACK TRANSACTION;
/*Rethrow the error. The msg_str parameter will contain the original error information*/
RAISERROR( @MessageTemplate /*msg_str parameter as message format template*/
,@ErrorSeverity /*severity parameter*/
,@RaisErrorState /*state parameter*/
,@ErrorNumber /*argument: original error number*/
,@ErrorSeverity /*argument: original error severity*/
,@ErrorState /*argument: original error state*/
,@ErrorProcedure /*argument: original error procedure name*/
,@ErrorLine /*argument: original error line number*/
,@ErrorMessage /*argument: original error message*/
);
END; /*Error Handling*/
END /*Stored Procedure*/
GO