Test execution never ends when Ctrl+C key hit in MTP mode

[radim-bernatik-veeam]

When using NUnit tests with MTP mode the execution of tests is not terminated when CTRL+C key is pressed in the console. It is visible that CtrlCIssue.UnitTests.Test event is raised, but test engine is running forever from that point. If no CTRL+C is pressed, test session ends in 5 seconds as there is only one test with 5s sleep code.

I tried the same case with MSTest tests, to identify if the issue is in MTP code or NUnit (adapter). When MSTest used instead of NUnit, behavior is correct. After CTRL+C the test session is finished and properly reported. When NUnit is used, I have to kill the process externally (via Task Manager or PowerShell).

How to simulate:

1. Compile the example below
2. Execute CtrlCIssue.exe --no-ansi --output Detailed command (using no-ANSI console reporter for better logging in the example, MTP logger has no impact)
3. Right after execution when NUnit3TestExecutor discovered 1 of 1 NUnit test cases using Current Discovery mode, Non-Explicit run message is displayed, hit the CTRL+C key.
4. After few second warning exception is displayed The operation was canceled., but execution never stops. The message Canceling the test session... comes from MTP when Console.CancelKeyPress event is raised.

Screenshot from the execution

CtrlCIssueMSTest.csproj

<Project Sdk="Microsoft.NET.Sdk">
	<PropertyGroup>
		<TargetFramework>net8</TargetFramework>
		<IsPackable>false</IsPackable>
		<IsTestProject>true</IsTestProject>
		<EnableNUnitRunner>true</EnableNUnitRunner>
		<TestingPlatformDotnetTestSupport>true</TestingPlatformDotnetTestSupport>
		<OutputType>Exe</OutputType>
	</PropertyGroup>
	<ItemGroup>
		<PackageReference Include="coverlet.collector" Version="6.0.0" />
		<PackageReference Include="Microsoft.NET.Test.Sdk" Version="18.0.1" />
		<PackageReference Include="Microsoft.Testing.Extensions.Telemetry" Version="2.0.2" />
		<PackageReference Include="Microsoft.Testing.Extensions.TrxReport" Version="2.0.2" />
		<PackageReference Include="Microsoft.Testing.Extensions.VSTestBridge" Version="2.0.2" />
		<PackageReference Include="Microsoft.Testing.Platform" Version="2.0.2" />
		<PackageReference Include="Microsoft.Testing.Platform.MSBuild" Version="2.0.2" />
		<PackageReference Include="NUnit" Version="3.12.0" />
		<PackageReference Include="NUnit.Analyzers" Version="3.8.0" />
		<PackageReference Include="NUnit3TestAdapter" Version="5.1.0" />
	</ItemGroup>
</Project>

UnitTests.cs

using NUnit.Framework;
using System.Threading;

namespace CtrlCIssue
{
    [TestFixture]
    public class UnitTests
    {
        [Test]
        public void Test()
        {
            Thread.Sleep(5000);
        }
    }
}

[OsirisTerje]

@radim-bernatik-veeam There are breaking changes between MTP 2 and MTP 1. Adapter 5.1 use MTP 1, and adapter 6 uses MTP 2.

I assume you see the same when upgrading the adapter to v.6.0.0 ?

PS: I am soon pushing out an alpha of the v6 adapter (6.0.1-alpha.5 ) , please check that also when it arrives (on myget).

[radim-bernatik-veeam]

@OsirisTerje I have checked several combination. Nothing works (execution not terminated after CTRL+C):

• Adapter 5.1.0, MTP 2.0.2 (original case)
• Adapter 5.2.0, MTP 1.9.1
• Adapter 6.0.0, MTP 2.0.2
• Adapter 6.0.0, MTP 1.9.1 is not possible due to package downgrade (I did not forced to test this, it makes no sense anyway)

[OsirisTerje]

@radim-bernatik-veeam

Can you try this one:

NUnit3TestAdapter.6.0.1-alpha.5.zip

Sorry, try .6

NUnit3TestAdapter.6.0.1-alpha.6.zip

Set the NUnit.Verbosity to 5, it should then show a Trace statement that it has reached StopRun. If you see it, then it is the engine that can't stop the run. If you dont see it, it is either MTP who doesnt send it on, or something else in the adapter that swallows it.

PS: You should not need to reference the MTP packages, the adapter have dependencies to them anyway.

[radim-bernatik-veeam]

@OsirisTerje I tried 6.0.1-aplha.6 as you suggested. I have removed the MTP reference from CSPROJ to simplify it. There is a message Trace: Cancel - starting to StopRun.

Full result:

d:\Git\MTP>CtrlCIssue\bin\Debug\net8\CtrlCIssue.exe --no-ansi --output Detailed --results-directory TestResults --settings D:\Git\IntegrationTests.runsettings
Microsoft.Testing.Platform v2.0.2+88c9fc53a3 (UTC 11/11/2025) [win-x64 - net8.0]
Setting: MaxCpuCount =
Setting: MaxCpuCount = -1
Setting: ResultsDirectory = d:\Git\MTP\TestResults
Setting: TargetPlatform =
Setting: TargetFrameworkVersion =
Setting: TestAdapterPaths =
Setting: CollectSourceInformation = False
Setting: DisableAppDomain = False
Setting: DisableParallelization = False
Setting: AllowParallelWithDebugger = False
Setting: DesignMode = False
Setting: CollectDataForEachTestSeparately = False
Setting: WorkDirectory =
Setting: Where =
Setting: DefaultTimeout =
Setting: DefaultTimeout = 0
Setting: NumberOfTestWorkers =
Setting: NumberOfTestWorkers = -1
Setting: ShadowCopyFiles = False
Setting: UseVsKeepEngineRunning = False
Setting: BasePath =
Setting: PrivateBinPath =
Setting: TestOutputXml =
Setting: TestOutputXmlFileName =
Setting: OutputXmlFolderMode =
Setting: NewOutputXmlFileForEachRun = False
Setting: RandomSeed =
Setting: RandomSeed =
Setting: DefaultTestNamePattern =
Setting: ShowInternalProperties = False
Setting: UseParentFQNForParametrizedTests = False
Setting: UseNUnitIdforTestCaseId = False
Setting: ConsoleOut =
Setting: ConsoleOut = 1
Setting: StopOnError = False
Setting: UseNUnitFilter = True
Setting: IncludeStackTraceForSuites = True
Setting: IncludeStackTrace = True
Setting: EnsureAttachmentFileScheme = False
Setting: SkipExecutionWhenNoTests = False
Setting: ThrowOnEachFailureUnderDebugger = False
Setting: DiscoveryMethod =
Setting: SkipNonTestAssemblies = True
Setting: AssemblySelectLimit =
Setting: AssemblySelectLimit = 2000
Setting: ExplicitMode =
Setting: DumpXmlTestDiscovery = False
Setting: DumpXmlTestResults = False
Setting: DumpVsInput = False
Setting: FreakMode = False
Setting: InternalTraceLevel =
Setting: Debug = False
Setting: DebugExecution = False
Setting: DebugDiscovery = False
Setting: DisplayName =
Setting: FullnameSeparator =
Setting: PreFilter = False
Setting: VsTestCategoryType =
Setting: MapWarningTo =
Setting: UseTestNameInConsoleOutput = False
.Net/ .Net Core adapter running from d:\Git\MTP\CtrlCIssue\bin\Debug\net8\NUnit3.TestAdapter.dll
Current directory: d:\Git\MTP
NUnit Adapter 6.0.0.0: Test execution started
KeepAlive: False
UseVsKeepEngineRunning: False
EnableShutdown: True
RunTests by IEnumerable<string>,(1 entries), called from d:\Git\MTP\CtrlCIssue\bin\Debug\net8\CtrlCIssue.dll
Runtype: CommandLineCurrentNUnit
Running all tests in d:\Git\MTP\CtrlCIssue\bin\Debug\net8\CtrlCIssue.dll
Workdir set to: d:\Git\MTP\CtrlCIssue\bin\Debug\net8
.Net/ .Net Core adapter running from d:\Git\MTP\CtrlCIssue\bin\Debug\net8\NUnit3.TestAdapter.dll
Current directory: d:\Git\MTP\CtrlCIssue\bin\Debug\net8
Execution engine run time with filter length 9 :Elapsed: 00:00:00.05
Filter: <filter/>
   NUnit3TestExecutor discovered 1 of 1 NUnit test cases using Current Discovery mode, Non-Explicit run
Converting test cases  :Elapsed: 00:00:00.00
Trace: Cancel - starting to StopRun

Canceling the test session...

[+0/x0/?0] CtrlCIssue.dll (net8.0|x64) - Test (3s)

Error processing Test event for CtrlCIssue.UnitTests.Test
System.OperationCanceledException: The operation was canceled.
   at System.Threading.CancellationToken.ThrowOperationCanceledException()
   at System.Threading.CancellationToken.ThrowIfCancellationRequested()
   at Microsoft.Testing.Extensions.VSTestBridge.ObjectModel.FrameworkHandlerAdapter.RecordEnd(TestCase testCase, TestOutcome outcome) in /_/src/Platform/Microsoft.Testing.Extensions.VSTestBridge/ObjectModel/FrameworkHandlerAdapter.cs:line 120
   at NUnit.VisualStudio.TestAdapter.NUnitEventListener.TestFinished(INUnitTestEventTestCase resultNode) in C:\repos\nunit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnitEventListener.cs:line 178
   at NUnit.VisualStudio.TestAdapter.NUnitEventListener.OnTestEvent(String report) in C:\repos\nunit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnitEventListener.cs:line 85

Canceling the test session...

[+0/x0/?0] CtrlCIssue.dll (net8.0|x64) - Test (6s)

[+0/x0/?0] CtrlCIssue.dll (net8.0|x64) - Test (9s)

[+0/x0/?0] CtrlCIssue.dll (net8.0|x64) - Test (12s)

[OsirisTerje]

@radim-bernatik-veeam Did you still have hanging process ?

@Youssef1313 Is that last exception expected ?

[radim-bernatik-veeam]

@OsirisTerje Yes, the process still hangs. You can see to in the result, test itself took 5s, but in the log is 12s. I had to kill the process externally.

[radim-bernatik-veeam]

@OsirisTerje I made another test. We are using quite old version of NUnit 3.12.0. When I upgraded to 3.13.0, problem disappeared. Version 3.14.0 and latest 4.4.0 works as well.

So I guess we will close this ticket, because it is probably not in adapter, but old version of NUnit itself. Or you have another opinion?

[OsirisTerje]

Yes, I can repro it on the latest......

Not sure why it works on 3,13 though....

[OsirisTerje]

@stevenaw Can this be related to #5096

[stevenaw]

I haven't had the chance to experiment with this scenario myself but I suspect either #5096 or #1821
The latter may be more likely (in my opinion) if we're trying to cancel the whole test run here.

@radim-bernatik-veeam What is the behavior without MTP?

The cancellation mechanisms were reworked in Nunit 4 to account for threadabort no longer being supported for modern .NET runtimes which could explain the differences observed between NUnit 3.14 and 4.4.

[radim-bernatik-veeam]

@stevenaw I performed the tests using command dotnet test CtrlCIssue\bin\Debug\net8\CtrlCIssue.dll and after hitting CTRL+C the process were terminated immediately.

[OsirisTerje]

@stevenaw @radim-bernatik-veeam
The fix for NUnit Issue #5096 in PR #5105 also fix this issue, and cancel the run. When running with the code from the PR, the result is as shown below.

We should fix up the exception messages here too in the adapter, and make this cleaner. I'll make a separate issue for that job.