Preserve CTRF duplicate results and test attachments

[Amaury Levé (Evangelink)]

Summary

• preserve every terminal test execution when multiple results share an MTP UID instead of inferring retry/flaky relationships
• serialize per-test FileArtifactProperty values as schema-compliant CTRF attachments with MIME inference, fallback metadata, and descriptions
• update focused unit and acceptance coverage for duplicate UIDs and real file artifacts

Testing

• Microsoft.Testing.Extensions.UnitTests: 52 CTRF reporter tests passed on net8.0
• Microsoft.Testing.Platform.Acceptance.IntegrationTests: 15 CTRF acceptance cases passed across net462, net8.0, and net10.0

Fixes #10764

[Copilot]

Pull request overview

Preserves duplicate-UID CTRF executions and adds test attachment serialization, addressing #10764.

Changes:

• Removes UID-based retry collapsing.
• Adds MIME-aware CTRF attachments.
• Expands unit and acceptance coverage.

Show a summary per file

File	Description
CapturedAttachment.cs	Adds attachment DTO.
CapturedTestResult.cs	Stores captured attachments.
TestResultCapture.cs	Captures attachment metadata and MIME types.
CtrfReportEngine.JsonTestWriter.cs	Serializes CTRF attachments.
CtrfReportEngine.JsonSerializer.cs	Counts and emits every execution.
CtrfReportEngine.TestCollapsing.cs	Removes UID-based collapsing.
InternalAPI.Unshipped.txt	Tracks new internal APIs.
CtrfReportEngineTests.cs	Tests attachments and duplicate UIDs.
CtrfReportTests.cs	Adds end-to-end attachment and duplicate coverage.

Review details

💡 Configure MCP servers for context-aware, tailored reviews. Learn more in the docs.

• Files reviewed: 9/9 changed files
• Comments generated: 2
• Review effort level: Balanced

[Copilot]

Review details

• Files reviewed: 11/11 changed files
• Comments generated: 3
• Review effort level: Balanced

[Copilot]

Review details

Suppressed comments (1)

src/Platform/Microsoft.Testing.Extensions.CtrfReport/CtrfReportEngine.JsonSerializer.cs:104

• Hard-coding flaky to zero reintroduces #10292 for MSTest [Retry]. These updates carry RetryAttemptProperty (MSTestTestNodeConverter.cs:116-122), which was added specifically so CTRF can emit retryAttempts/flaky; its contract still documents that behavior (RetryAttemptProperty.cs:12-16). Stop UID-only inference for untagged duplicate UIDs, but retain retry collapsing for explicitly tagged attempt sequences. As written, a fail-then-pass retry is incorrectly reported as two unrelated tests rather than one flaky pass.

            // MTP UIDs are not unique per execution, so they cannot establish retry
            // relationships. Keep flaky at zero until explicit attempt correlation is
            // available rather than dropping duplicate-UID results or inventing retries.
            writer.WriteNumber("flaky", 0);

• Files reviewed: 11/11 changed files
• Comments generated: 0 new
• Review effort level: Balanced

[Brad Wilson (bradwilson)]

FYI, I used this list for our default mappings: https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/MIME_types/Common_types

We're going in the opposite direction, since we are combining attachment name + media type into a filename, so we're mapping media types to file extensions, but it seems like you could use roughly the same list. We also do an on-Windows-only fallback to look things up in the registry under HKEY_CLASSES_ROOT.