Deduplicate CIEnvironmentDetector across TestFramework and Platform

[Evangelink]

Fixes #8985.

Summary

The CIEnvironmentDetector class was duplicated nearly verbatim in src/TestFramework/TestFramework/Internal/ and src/Platform/Microsoft.Testing.Platform/Helpers/, with the same arrays of CI environment variable names and the same IsCIEnvironment() logic in each copy. The two had already begun to drift (XML doc shape, attribute usage), and any future CI provider addition would have required two parallel edits.

Changes

• src/Platform/Microsoft.Testing.Platform/Helpers/CIEnvironmentDetector.cs is now the single source of truth. Small #if TESTFRAMEWORK_CI_DETECTOR blocks toggle the real, intentional differences between the Platform and TestFramework variants:
  • namespace (Microsoft.Testing.Platform.Helpers vs Microsoft.VisualStudio.TestTools.UnitTesting)
  • [Embedded] / [ExcludeFromCodeCoverage] attributes (Platform only)
  • public vs internal /* for testing */ constructor
  • static Instance helper (TestFramework only, consumed by CIConditionAttribute)
  • RoslynString.IsNullOrEmpty (Platform — banned-symbol convention) vs string.IsNullOrEmpty (TestFramework)
• src/TestFramework/TestFramework/Internal/CIEnvironmentDetector.cs deleted.
• src/TestFramework/TestFramework/TestFramework.csproj now links the canonical file from Platform via <Compile Include="…/Platform/…/CIEnvironmentDetector.cs" Link="Internal/CIEnvironmentDetector.cs" /> and defines TESTFRAMEWORK_CI_DETECTOR. This mirrors the existing pattern already used for RoslynHashCode.cs in the same csproj, and matches what Microsoft.Testing.Extensions.Telemetry.csproj already does for this file.
• eng/vendored-files.json updated: removed the now-redundant testframework-ci-environment-detector entry and expanded the platform-ci-environment-detector note to document the new linked-file relationship.

Net diff: 4 files changed, 43 insertions(+), 133 deletions(-).

Verification

• dotnet build for Microsoft.Testing.Platform, Microsoft.Testing.Extensions.Telemetry, and MSTest.TestFramework: 0 warnings / 0 errors across netstandard2.0, net462, net8.0, net9.0.
• TestFramework.UnitTests on net8.0 (entire suite): 1189 / 1189 passed, including all 17 CIEnvironmentDetectorTests and all 4 CIConditionAttributeTests.

[Copilot]

Pull request overview

This PR removes a duplicated CIEnvironmentDetector implementation by making src/Platform/Microsoft.Testing.Platform/Helpers/CIEnvironmentDetector.cs the canonical source and linking it into MSTest.TestFramework, using #if TESTFRAMEWORK_CI_DETECTOR to toggle the intentional TestFramework-vs-Platform differences.

Changes:

• Linked the Platform CIEnvironmentDetector.cs into MSTest.TestFramework and added the TESTFRAMEWORK_CI_DETECTOR compilation constant.
• Removed the in-tree duplicated src/TestFramework/TestFramework/Internal/CIEnvironmentDetector.cs.
• Updated the canonical Platform CIEnvironmentDetector to support both variants via conditional compilation.
• Updated eng/vendored-files.json to reflect the dedup/linking relationship (but see comment about the define name).

Show a summary per file

File	Description
src/TestFramework/TestFramework/TestFramework.csproj	Links the canonical detector file and defines TESTFRAMEWORK_CI_DETECTOR for the TestFramework-specific variant.
src/TestFramework/TestFramework/Internal/CIEnvironmentDetector.cs	Removes the duplicated TestFramework copy.
src/Platform/Microsoft.Testing.Platform/Helpers/CIEnvironmentDetector.cs	Becomes the single source of truth with #if TESTFRAMEWORK_CI_DETECTOR toggles for namespace/attributes/ctor/Instance/IsNullOrEmpty behavior.
eng/vendored-files.json	Updates vendored-file metadata to reflect the new single-source/linking setup.

Copilot's findings

• Files reviewed: 4/4 changed files
• Comments generated: 1

[Evangelink]

Note

🤖 Automated review by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review workflow. To request a follow-up action, reply by tagging @copilot directly.

#	Dimension	Verdict
17	Documentation Accuracy	🟢 1 NIT

✅ 21/22 dimensions clean.

• Documentation — vendored-files.json notes say "IS_CORE_MTP define" but the toggle define is TESTFRAMEWORK_CI_DETECTOR

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Design notes (non-blocking):

The single-source-of-truth approach via <Compile Link=...> + TESTFRAMEWORK_CI_DETECTOR is well-established in this codebase (the RoslynHashCode.cs link uses the same pattern). The six #if blocks are easy to follow and each one is necessary. The DefineConstants PropertyGroup placement after the ItemGroup in TestFramework.csproj is valid MSBuild — properties are evaluated before the compiler is invoked regardless of document order.

Functional equivalence is preserved: string.IsNullOrEmpty (TestFramework branch) and RoslynString.IsNullOrEmpty (Platform branch) both delegate to string.IsNullOrEmpty — no behavioral delta. The EnvironmentWrapper.Instance reference in the Instance property resolves to the correct type in each compilation context because both build the file under their own namespace.

🤖 Automated content by GitHub Copilot. Posted via a maintainer's GitHub token, so it appears under their account — the account owner did not write or approve this content personally. Generated by the Expert Code Review (on PR ready) workflow.{ai_credits_suffix} · ◷

[Evangelink]

[NIT] Documentation Accuracy

The notes field says "toggled via the IS_CORE_MTP define" but the actual define that gates the TestFramework variant is TESTFRAMEWORK_CI_DETECTOR. IS_CORE_MTP is a separate, unrelated symbol used only inside Microsoft.Testing.Platform.csproj to guard PlatformResources.cs.

A future maintainer searching for #if IS_CORE_MTP to understand how this file is toggled will come up empty.

Recommendation: Change IS_CORE_MTP → TESTFRAMEWORK_CI_DETECTOR in this notes string to match the actual define in TestFramework.csproj and the comment at the top of the linked source file.