Fix Flesch-Kincaid grade 9 threshold

[benitoalba]

Fixes #1797.

Summary

• Treat Flesch-Kincaid grade 9 as passing and only grades above 9 as readability failures.
• Align the AJAX post-grade and REST simplified-summary thresholds on > 9.
• Correct the misleading threshold comment and add grade 9/10 regression coverage for both paths.

Root cause

Two readability paths used boundary conditions equivalent to >= 9, while the related checks and user-facing copy define a failure as a reading level higher than grade 9. A nearby comment also described the correct > 9 comparison as "grade 9+."

Validation

• Focused PHPUnit suite: 11 tests, 46 assertions.
• Full PHPUnit suite: 878 tests, 1,880 assertions, 15 skipped.
• PHPCS on all four changed files.
• PHP lint across 226 files.
• git diff --check.

Checklist

• PR is linked to the main issue in the repo.
• Tests are added that cover changes.

Summary by CodeRabbit

• Bug Fixes

  • Updated readability scoring so grade 9 passes the threshold, while only grades above 9 are marked as failing.
  • Applied the corrected threshold consistently across readability messages, icons, and simplified-summary results.

• Tests

  • Added coverage for grade 9 passing and grade 10 failing in readability checks.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 9519618b-99ee-4617-b222-1060029f3615

📥 Commits

Reviewing files that changed from the base of the PR and between 0053fb7 and ba28f91.

📒 Files selected for processing (1)

• tests/phpunit/includes/classes/RestApiSidebarDataTest.php

🚧 Files skipped from review as they are similar to previous changes (1)

• tests/phpunit/includes/classes/RestApiSidebarDataTest.php

---

📝 Walkthrough

Walkthrough

Readability failure checks now use a strict grade-above-9 threshold in AJAX and REST responses. PHPUnit tests cover grade 9 as passing and grade 10 as failing.

Changes

Readability threshold alignment

Layer / File(s)	Summary
Apply strict grade threshold admin/class-ajax.php, includes/classes/class-rest-api.php	Readability failures now require a grade above 9, including simplified-summary results. The REST API comment documents the grade 10+ threshold.
Validate grade boundary tests/phpunit/Admin/AjaxReadabilityTest.php, tests/phpunit/includes/classes/RestApiSidebarDataTest.php	PHPUnit coverage verifies grade 9 passes and grade 10 fails in AJAX and REST readability behavior. Test cleanup removes simplified-summary metadata.

Estimated code review effort: 2 (Simple) | ~10 minutes

Possibly related PRs

• equalizedigital/accessibility-checker#1725: Modifies the same readability paths and grade normalization used by these threshold checks.

Suggested reviewers: pattonwebz

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly identifies the Flesch-Kincaid grade 9 threshold fix, which is the primary change.
Linked Issues check	✅ Passed	The changes implement issue #1797 by applying >9 comparisons, correcting the comment, and adding grade 9 and 10 regression tests.
Out of Scope Changes check	✅ Passed	All code and test changes directly support the readability threshold fix and its regression coverage; no unrelated changes are present.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@tests/phpunit/includes/classes/RestApiSidebarDataTest.php`:
- Around line 161-163: Update the test cleanup flow in tearDown() for the shared
self::$post_id fixture to delete the _edac_simplified_summary metadata after
each test, ensuring test_get_readability_data_uses_above_ninth_grade_threshold()
cannot affect later tests.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

---

ℹ️ Review info

⚙️ Run configuration

Configuration used: Path: .coderabbit.yaml

Review profile: CHILL

Plan: Pro Plus

Run ID: 0c03123b-c37e-4810-acfe-ccb447df1a8b

📥 Commits

Reviewing files that changed from the base of the PR and between b2fcc98 and 0053fb7.

📒 Files selected for processing (4)

• admin/class-ajax.php
• includes/classes/class-rest-api.php
• tests/phpunit/Admin/AjaxReadabilityTest.php
• tests/phpunit/includes/classes/RestApiSidebarDataTest.php