Test: Classify and enforce unit test environments by filename

[ciampo]

Part of #80855.

What?

Classify every unit test by the environment in its filename, and make that filename select the environment:

• *.test.* runs in Node.js.
• *.jsdom.test.* runs in jsdom.
• *.browser.test.* runs in a real browser.

This PR does not move tests from Jest to Vitest. The migration manifest still decides which runner owns a test; the filename now decides which environment that runner uses.

Why?

Vitest uses Node.js by default, while Jest previously ran every test in jsdom. Explicit filenames prevent tests from silently running in the wrong environment during the migration.

The convention is also enforced for future changes. The routing check verifies that every discovered test belongs to exactly one runner and the correct filename-selected project. Per-file @jest-environment and @vitest-environment overrides are rejected.

How?

• Rename tests that need the DOM to *.jsdom.test.*, while keeping Node-compatible tests unsuffixed and existing Browser Mode tests as *.browser.test.*.
• Split Jest into Node.js and jsdom projects selected by filename.
• Make the routing check compare each Jest and Vitest project's actual inventory with the filename-derived inventory.
• Rename matching snapshots and update documentation and exact-path tooling references.

Files that mix DOM-only and browser-dependent assertions are intentionally not split here. A later Browser Mode PR will split them after Browser Mode is enabled for those tests, so the new *.browser.test.* files run in Chromium instead of Jest's jsdom environment.

Testing Instructions

• Confirm the unit tests, npm run test:unit:routing, and npm run test:unit:conventions pass. The routing check must report every discovered test in exactly one runner and the correct filename-selected project; the four Jest shards must cover the complete inventory once.
• Review the classifications: use Browser Mode where real browser behavior is necessary, jsdom for deterministic DOM-only behavior, and Node.js otherwise. Confirm that matching snapshots and exact-path tooling references moved with each renamed test.

Testing Instructions for Keyboard

Not applicable. This PR changes test infrastructure and filenames, with no user-facing or keyboard behavior changes.

Use of AI Tools

Codex assisted with the environment audit, mechanical renames, enforcement, reference updates, verification, and adversarial self-review. The author reviewed the resulting changes and test output.

[github-actions]

Size Change: 0 B

Total Size: 7.92 MB

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[github-actions]

Flaky tests detected in 29de986.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/33212055973
📝 Reported tests:

Should save the changes in /test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js, passed after 2 failed attempts.

TimeoutError: page.waitForFunction: Timeout 10000ms exceeded.
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js:34:14
TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for locator('role=button[name="Visual"i]')

    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/plugins/wp-editor-meta-box.spec.js:33:55

awareness cursor tracks all positions through a bolded word without sticking at formatting boundaries in /test/e2e/specs/editor/collaboration/collaboration-awareness-cursor-position.spec.ts, passed after 1 failed attempt.

Error: Awareness cursor should be visible at offset 0

expect(received).not.toBe(expected) // Object.is equality

Expected: not -1
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/collaboration/collaboration-awareness-cursor-position.spec.ts:124:10

shows pattern summary fields in the post editor in /test/e2e/specs/editor/various/post-summary-dataform/post-summary.spec.js, passed after 1 failed attempt.

Error: apiRequestContext.fetch: socket hang up
Call log:
  - → GET http://localhost:8889/wp-json/wp/v2/blocks?per_page=100&status=publish%2Cfuture%2Cdraft%2Cpending%2Cprivate%2Ctrash
    - user-agent: Playwright/1.62.1 (x64; ubuntu 24.04) node/20.20 CI/1
    - accept: */*
    - accept-encoding: gzip,deflate,br
    - X-WP-Nonce: cd764cce96
    - cookie: wordpress_test_cookie=WP%20Cookie%20check; wordpress_logged_in_23778236db82f19306f247e20a353a99=admin%7C1788125105%7CoaVhnmzWAl3JAmglT7TAr1R5PA7AodiWkg6vp4WbX5N%7C57fe1f9a3845ef25d0d5e8284a6cfe12c72c902c5a268de962dbc43bfb2bada2; wp-settings-time-1=1787952689

    at RequestUtils.rest (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/rest.ts:112:39)
    at RequestUtils.deleteAllBlocks (/home/runner/work/gutenberg/gutenberg/packages/e2e-test-utils-playwright/src/request-utils/blocks.ts:23:28)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/various/post-summary-dataform/post-summary.spec.js:25:23

[github-actions]

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Co-authored-by: ciampo <mciampini@git.wordpress.org>
Co-authored-by: mirka <0mirka00@git.wordpress.org>

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