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.

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[adamsitnik]

/azp list

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[adamsitnik]

/azp run runtime-extra-platforms

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[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

[Copilot]

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

Fixed in 935dd2d.

I added a class-local AllSeekModes forwarder in the System.Memory conformance test classes so xUnit MemberData resolution succeeds under trimmed mobile runs:

• ROSequenceStreamConformanceTests
• NativeReadOnlyMemoryStreamConformanceTests
• NativeWritableMemoryStreamConformanceTests

I also ran targeted System.Memory conformance classes and they pass locally.