Mark memory-intensive Utf8JsonWriterTests for OuterLoop and 64-bit only

[Copilot]

• Locate and examine the failing tests in Utf8JsonWriterTests.cs
• Add OuterLoop and ConditionalFact(64-bit only) attributes to WritePropertyWithExtremelyLongName_ThrowsArgumentException
• Add OuterLoop and ConditionalFact(64-bit only) attributes to WriteValueWithExtremelyLongValue_ThrowsArgumentException
• Verify the changes follow the existing pattern in the file
• Build and test the System.Text.Json library
• Confirm tests compile successfully
• Update to use PlatformDetection.Is64BitProcess instead of Environment.Is64BitProcess

Original prompt

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This section details on the original issue you should resolve

<issue_title>Utf8JsonWriterTests.WriteValueWithExtremelyLongValue_ThrowsArgumentException test fails with OutOfMemoryException</issue_title>
<issue_description>## Build Information
Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1180196
Build error leg or test failing: System.Text.Json.Tests.Utf8JsonWriterTests.WritePropertyWithExtremelyLongName_ThrowsArgumentException
Pull request: #120858

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["System.Text.Json.Tests.Utf8JsonWriterTests.WriteValueWithExtremelyLongValue_ThrowsArgumentException","OutOfMemoryException"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1180196
Error message validated: [System.Text.Json.Tests.Utf8JsonWriterTests.WriteValueWithExtremelyLongValue_ThrowsArgumentException OutOfMemoryException]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 10/20/2025 9:30:10 PM UTC

Report

Build	Definition	Test	Pull Request
1180337	dotnet/runtime	System.Text.Json.Tests.Utf8JsonWriterTests.WritePropertyWithExtremelyLongName_ThrowsArgumentException	#120917
1180312	dotnet/runtime	System.Text.Json.Tests.Utf8JsonWriterTests.WritePropertyWithExtremelyLongName_ThrowsArgumentException	#120041
1180275	dotnet/runtime	System.Text.Json.Tests.Utf8JsonWriterTests.WriteValueWithExtremelyLongValue_ThrowsArgumentException	#120272
1180196	dotnet/runtime	System.Text.Json.Tests.Utf8JsonWriterTests.WritePropertyWithExtremelyLongName_ThrowsArgumentException	#120858

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
4	4	4

<agent_instructions>Please mark this test for outerloop and 64-bit only</agent_instructions>

Comments on the Issue (you are @copilot in this section)

@jkotas Regression introduced by #120731

cc @eiriktsarpalis @stephentoub </comment_new>

Fixes #120918

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[Copilot]

Pull Request Overview

This PR addresses OutOfMemoryException failures in two Utf8JsonWriter tests by restricting them to run only in 64-bit outer loop scenarios. Both tests allocate extremely large strings (170 million characters) which can exhaust memory in resource-constrained environments or 32-bit processes.

Key changes:

• Added [ConditionalFact(typeof(Environment), nameof(Environment.Is64BitProcess))] to ensure tests only run on 64-bit processes
• Added [OuterLoop] attribute to move tests out of default CI runs