Refactor Test TDS Servers. Expand functional testing of connection pooling and transient failures. #3488

mdaigle · 2025-07-17T19:04:56Z

Description

The TDS.Servers project provides mocked server implementations for a variety of use cases. The construction and endpoint initialization flows for these mock servers was complicated and resulted in duplicated code across TDS.Servers, FunctionalTests, and ManualTests. This PR consolidates endpoint initialization and makes test server constructor parameters more explicit (no more defaults buried a few layers deep).

One downside of this approach is that it's now slightly harder to get the connection string for a test server. Before, some servers had a ConnectionString property you could access. The issue with these connection strings is they had a lot of non-standard default behavior coded into them at the time they were constructed. This makes it hard to understand which properties you're actually using when connecting to a test server. With my changes, you now need to manually construct a connection string using SqlConnectionStringBuilder and explicitly set connection parameters. Any parameters you don't set use the stock connection string defaults.

Testing

I added some testing around pool invalidation during failover and routing behavior during transient errors.

…ailover-tds-server

…ass.

paulmedynski

Looks good to me, with a few suggestions.

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlConnectionBasicTests.cs

src/Microsoft.Data.SqlClient/tests/FunctionalTests/SqlConnectionReadOnlyRoutingTests.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/AuthenticatingTDSServer.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTDSServer.cs

paulmedynski · 2025-07-18T11:22:57Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TdsServer.cs

+        public TdsServer() : this(new TdsServerArguments())
+        {
+        }
+        /// <summary>


Missing a blank line here.

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TdsServer.cs

…ut. Clean up transient error server.

…p where they're supposed to, not just side effects.

paulmedynski

A few tidying-up suggestions.

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDSServerEndPointConnection.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TransientFaultTdsServer.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TdsServer.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TransientTimeoutTdsServer.cs

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TransientTimeoutTdsServerArguments.cs

…ailover-tds-server

paulmedynski

A couple of suggestions.

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDSServerEndPointConnection.cs

paulmedynski · 2025-08-21T11:25:42Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TransientDelayTdsServer.cs

            if (Arguments.IsEnabledPermanentTimeout ||
-                (Arguments.IsEnabledTransientTimeout && RequestCounter < 1)) // Fail first time, then connect
+                (Arguments.IsEnabledTransientTimeout && RequestCounter < 1))


RequestCounter < Arguments.RepeatCount ?

…NIR.

…ion string settings and fix tests.

paulmedynski

Still some outstanding requests from earlier PRs as well. I will go back through them and see if they have been addressed.

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTdsServer.cs

src/Microsoft.Data.SqlClient/tests/UnitTests/ADPHelper.cs

…ailover-tds-server

paulmedynski · 2025-09-05T14:24:18Z

Two small comments remain. Should this convereted from a draft now?

Copilot

Pull Request Overview

This PR refactors the Test TDS Servers infrastructure by consolidating endpoint initialization and improving the construction flow for mock servers. The changes eliminate duplicated code across TDS.Servers, FunctionalTests, and ManualTests while making constructor parameters more explicit rather than hiding defaults in nested calls.

Key changes include:

Standardized naming from "TDS" to "Tds" across server classes for consistency
Replaced properties with field initializers for server arguments to make defaults explicit
Simplified endpoint initialization by removing auto-generated connection strings
Added new transient delay and error servers for improved testing scenarios
Consolidated connection string building using SqlConnectionStringBuilder

Reviewed Changes

Copilot reviewed 42 out of 42 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
`TransientTdsErrorTdsServerArguments.cs`	Renamed class and replaced properties with field initializers for clearer defaults
`TransientTdsErrorTdsServer.cs`	New server class for testing transient error scenarios with explicit error behavior
`TransientDelayTdsServerArguments.cs`	New arguments class for delay simulation testing
`TransientDelayTdsServer.cs`	New server class for simulating network delays during connections
`TdsServerArguments.cs`	Renamed class and converted properties to field initializers
`TdsServer.cs`	New simplified TDS server implementation
`GenericTdsServer.cs`	Refactored to use generics and added endpoint management
Connection test files	Updated to use new server construction patterns and explicit connection strings

Copilot · 2025-09-05T16:21:30Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/TransientTdsErrorTdsServer.cs

+        public void SetErrorBehavior(bool isEnabledTransientFault, uint errorNumber, int repeatCount = 1, string message = null)
+        {
+            Arguments.IsEnabledTransientError = isEnabledTransientFault;


The parameter name 'isEnabledTransientFault' is inconsistent with the field name 'IsEnabledTransientError'. Consider renaming the parameter to 'isEnabledTransientError' for consistency.

Suggested change

public void SetErrorBehavior(bool isEnabledTransientFault, uint errorNumber, int repeatCount = 1, string message = null)

{

Arguments.IsEnabledTransientError = isEnabledTransientFault;

public void SetErrorBehavior(bool isEnabledTransientError, uint errorNumber, int repeatCount = 1, string message = null)

{

Arguments.IsEnabledTransientError = isEnabledTransientError;

Copilot · 2025-09-05T16:21:31Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTdsServer.cs

+        public void Start([CallerMemberName] string methodName = "")
+        {
+            _endpoint = new TDSServerEndPoint(this) { ServerEndPoint = new IPEndPoint(IPAddress.Any, 0) };
+            _endpoint.EndpointName = methodName;
+            _endpoint.EventLog = Arguments.Log;
+            _endpoint.Start();
+        }


The Start method creates a new endpoint instance but doesn't check if one already exists. This could lead to resource leaks if Start is called multiple times. Consider adding a check for existing endpoint or making the method idempotent.

Copilot · 2025-09-05T16:21:31Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTdsServer.cs

@@ -880,5 +910,7 @@ private bool AreEqual(byte[] left, byte[] right)

            return left.SequenceEqual<byte>(right);
        }
+
+        public virtual void Dispose() => _endpoint?.Dispose();


The Dispose method only disposes the endpoint but doesn't set it to null or prevent further usage. Consider implementing the full IDisposable pattern with a disposed flag to prevent usage after disposal.

Copilot · 2025-09-05T16:21:32Z

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.EndPoint/TDSServerEndPointConnection.cs

    {
        /// <summary>
        /// Worker thread
        /// </summary>
-        protected Thread ProcessorThread { get; set; }
+        protected Task ProcessorTask { get; set; }


The ProcessorTask property should be disposed in the Dispose method to prevent potential resource leaks from unfinished tasks.

Copilot · 2025-09-05T16:21:32Z

...Microsoft.Data.SqlClient/tests/UnitTests/SimulatedServerTests/ConnectionRoutingTestsAzure.cs

+            using RoutingTdsServer router = new RoutingTdsServer(
+                new RoutingTdsServerArguments()
+                {
+                    //RoutingTCPHost = server.EndPoint.Address.ToString() == IPAddress.Any.ToString() ? IPAddress.Loopback.ToString() : server.EndPoint.Address.ToString(),


Remove commented-out code. If this logic might be needed later, consider documenting the reason or implementing it properly.

Suggested change

//RoutingTCPHost = server.EndPoint.Address.ToString() == IPAddress.Any.ToString() ? IPAddress.Loopback.ToString() : server.EndPoint.Address.ToString(),

mdaigle added 9 commits June 12, 2025 09:15

Add failover config options

8afcbc7

Test failovers

0007a10

Merge branch 'main' of github.com:dotnet/SqlClient into dev/mdaigle/f…

03b8e49

…ailover-tds-server

Test routing through a transient error.

2adf97c

Move startup to GenericTDSServer.

5113fa7

Remove duplicate server start code from ManualTests

522abba

Refactor failover param ownership. Fix pool invalidation test.

c41d0dc

Cleanup. Rename GenericTDSServer to differentiate from the generic cl…

922b3ef

…ass.

Rename classes to match style. Make GenericTdsServer<T> abstract.

6ef83d7

mdaigle added the Area\Tests Issues that are targeted to tests or test projects label Jul 17, 2025

paulmedynski requested changes Jul 18, 2025

View reviewed changes

mdaigle added 17 commits July 24, 2025 14:19

Fix connection string to use optional encryption.

47cbb48

Fix connection string to use optional encryption.

905bc5d

Add transient timeout server. Add regression test for transient timeo…

47aa3a3

…ut. Clean up transient error server.

Clean up tests. Add new retry/failover tests.

fe9e7e4

Add new retry/failover tests.

93ebf98

Added tests. Moved tests to UnitTests project. Removed failover repro.

04a4329

Restructure tests for readability.

ee9d157

Update tests to remove unneeded routing. Check that connections end u…

11d90db

…p where they're supposed to, not just side effects.

Review changes

846a493

Add TDS projects to compile set for UnitTests.

f08447a

fix tds projects inclusion

7780cdd

Fix test server disposal.

ed2285c

Remove tests for unsupported scenarios.

47b7bc2

Add comments for confusing behavior.

7532181

Rename files to match class names.

57aeb4d

Remove proj change.

12cbb82

Skip failing unit tests.

038a0cd

paulmedynski requested changes Aug 7, 2025

View reviewed changes

Rename test folder.

206216a

mdaigle added 7 commits August 14, 2025 15:26

Review changes

487fc26

Merge branch 'main' of github.com:dotnet/SqlClient into dev/mdaigle/f…

aeb0c29

…ailover-tds-server

Adjust tests based on multisubnetfailover setting.

767e99c

Improve test reliability.

4bda823

Make failover test more reliable.

a92dc51

Rename to fix missing file.

2638eca

Update tests to work on linux/mac

1492ead

paulmedynski requested changes Aug 21, 2025

View reviewed changes

mdaigle added 8 commits August 26, 2025 15:00

Add test for default TNIR setting in connection string.

d237176

Remove active issues and adapt tests to set multisubnetfailover and T…

0c03ddc

…NIR.

Enable setting localhost as an azure endpoint.

f379cba

Rename files and test cases for clarity. Rework some failover connect…

d1bb855

…ion string settings and fix tests.

Add azure routing tests.

e515abe

Serialize tests. Remove connection killing.

7d57e12

Add additional assertions.

2fe29ed

Add common test project to unit test restore targets.

5eee939

paulmedynski self-assigned this Sep 4, 2025

paulmedynski requested changes Sep 4, 2025

View reviewed changes

src/Microsoft.Data.SqlClient/tests/tools/TDS/TDS.Servers/GenericTdsServer.cs Show resolved Hide resolved

src/Microsoft.Data.SqlClient/tests/UnitTests/ADPHelper.cs Show resolved Hide resolved

mdaigle added 2 commits September 4, 2025 13:00

Mark tests as flaky and skip in the pipeline for now.

c020ddf

Merge branch 'main' of github.com:dotnet/SqlClient into dev/mdaigle/f…

32b9a10

…ailover-tds-server

Fix formatting.

71a0228

mdaigle marked this pull request as ready for review September 5, 2025 16:20

Copilot AI review requested due to automatic review settings September 5, 2025 16:20

mdaigle requested a review from a team as a code owner September 5, 2025 16:20

Copilot AI reviewed Sep 5, 2025

View reviewed changes

Refactor Test TDS Servers. Expand functional testing of connection pooling and transient failures. #3488

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Refactor Test TDS Servers. Expand functional testing of connection pooling and transient failures. #3488

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paulmedynski commented Sep 5, 2025

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Pull Request Overview

Reviewed Changes

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mdaigle commented Jul 17, 2025 •

edited by paulmedynski

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