[Mpdreamz]

First of a stack that moves the test suite onto Nullean.Snapshots: expected output lives in snapshots (inline in the test when small, .snapshots/ files when large) and is accepted with snap, instead of in chains of Contain assertions. This PR only makes the library available and adds the shared pieces; it converts no tests.

The ApiExplorer pilot (#4654) used Nullean.Snapshots.Html and .TUnit 0.2.0 in one project. Now every unit and integration test project gets 0.4.0 of the library:

• tests-shared/Elastic.Documentation.Testing (a library, outside tests/ because build/Targets.fs runs dotnet test on every csproj it finds there):
  • DocsHtml.Section() / Body(): the page content without the fixture's leading H1 and the htmx attributes on links. This merges what PrettyHtmlExtensions and HtmlAssertions each did.
  • DiagnosticsSnapshot.ToSnapshotText(): error|warning|hint file:line message, one line each. A clean run is the empty snapshot.
  • NavigationDump.ToText(): the navigation tree as indented text, index pages first, and a child whose Parent is wrong is flagged.
  • MockFileSystemDump.ToText(): every file under a mock-file-system folder, sorted, under === path === headers.
  • A scrubber for temp and repo paths, compiled into each test project (a module initializer in the library would only run once a test touched the assembly).
• snap as a local dotnet tool.
• CI: failed runs upload .artifacts/.snapshots/received/ (download it into the same place locally and run dotnet snap review). The build target fails on orphaned snapshots after a unit run.
• AGENTS.md describes the workflow; the PR review prompt no longer says the repo uses xUnit.

The five TestDiagnosticsCollector copies stay as they are. They differ in lifecycle (Write vs HandleItem), so merging them would change behaviour. DiagnosticsSnapshot works on any of them.

Checked

• All 18 unit projects pass; the ApiExplorer pilot snapshots pass unchanged on 0.4.0.
• dotnet run --project build -- unit-test passes, and fails when I plant an orphaned .verified.txt.
• The helpers have their own tests (SnapshotHelpersTests, inline snapshots). Breaking DocsHtml.Section() makes the HTML one fail.

Not checked

Windows and Linux. The CI artifact step has not run yet.

What CI added

The first CI run failed on Windows in four of the stacked PRs, which is what the path scrubbing here is for. A snapshot that holds a path must read the same on every machine, so:

• The repository and temp roots are replaced by {repo} and {temp}, and the rest of the path is written with forward slashes ({repo}\docs\index.md on Windows became {repo}/docs/index.md). The path ends at a colon, so file.md:3 keeps its line.
• A 32-hex-digit run under the temp folder (a Guid-named test folder) becomes {id}.
• Both are covered by tests, including a Windows-style root that runs on any OS. Removing the separator replacement makes that test fail.

The first version of the temp scrubber swallowed everything after the temp folder, including the file name, so a snapshot could record {temp} and lose the path. One such snapshot is regenerated in the Markdown PR.

All 18 unit projects also pass with CI, GITHUB_ACTIONS and GITHUB_REPOSITORY set and TZ=Asia/Tokyo, which is how I now check each PR locally before pushing.

🤖 Generated with Claude Code

[infra-vault-gh-plugin-prod]

Severity: P3 (Low)

NavigationDump.ToText is the only new shared helper with no test in SnapshotHelpersTests. Nothing checks that index pages come first, that indentation is right, that generic type names are trimmed, or that the [hidden], [island] and [wrong parent] flags appear. Later PRs in the stack will turn navigation tests into snapshots of this output, so a bug here would end up in accepted snapshots without anyone noticing. In particular, a broken [wrong parent] check would hide the exact regression it exists to catch. Please add a small inline-snapshot test that builds a tree with one mis-parented child.

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[Mpdreamz]

Added in #4739: three inline-snapshot tests over small fake navigation types (index first then children, indentation, [hidden] and [island], trimmed generic type names, a mis-parented child flagged [wrong parent], and an index page whose parent differs not being flagged). I mutated NavigationDump seven ways and each fails at least one test, including a [wrong parent] check that is never true.

[github-actions]

Docs preview (local build)

Handbook preview: https://docs-v3-preview.elastic.dev/elastic/docs-builder/pull/4719/

Sample changed pages:

• AGENTS.md