feat(ui5): Add QUnit best-practices skill

[plamenivanov91]

Adds the ui5-best-practices-qunit skill covering coding standards for OpenUI5/SAPUI5 unit test files. Follows the same structure as the OPA5 skill: a lean SKILL.md router plus three focused reference files loaded on demand by task type (writing new tests, modernizing existing ones, async patterns).

• SKILL.md: trigger description with literal user phrases, core rules table, quick-reference checklist
• references/writing-new-tests.md: module structure, AAA pattern, test naming, helpers, file setup (/*global QUnit */, sap.ui.define imports)
• references/modernizing-tests.md: var/const/let, bind, assert.async, Core.applyChanges, sinon sandbox, assert.expect, import cleanup, encoding fix, what-not-to-change guard table
• references/async-patterns.md: nextUIUpdate vs Core.applyChanges decision table (incl. fake-timer exceptions), waitForEvent, waitForRendering via addEventDelegate, when not to convert assert.async
• README.md: adds ui5-best-practices-qunit section
• plugin.json / .github/plugin/plugin.json: adds "qunit" keyword
• All files ISO 8859-1 compliant (no em dashes or non-ASCII)

JIRA: BGSOFUIPIRIN-7067

[flovogt]

@codeworrior Could you have a look at this QUnit best practices, please?

[codeworrior]

Overall LGTM, but IMO, there are still a few things to be clarified / added.

[plamenivanov91]

Here is the original qUnit improvement pilot change 6566798 (Gerrit ID).

[flovogt]

@plamenivanov91 please rebase

[codeworrior]

Again, well done! Only a few comments remaining.

[plamenivanov91]

As recommended by @pskelin , I installed skill-creator and tested the PR.

Here is a short AI summary of the test:

With skill-creator I ran a parallel eval (with-skill vs. baseline) across three scenarios using real openui5 test files as reference material.

The skill is effective at overriding Claude's default biases. Without it, Claude consistently falls back to pre-modern UI5 test patterns — Core.applyChanges() instead of nextUIUpdate(), assert.async() + callbacks instead of async/await, missing assert.expect(N), and var declarations. With the skill loaded, all of those are corrected reliably.

Eval 1 — writing a new async test from scratch (6/7 vs 2/7): The clearest win. The baseline used Core.applyChanges(), assert.async(), var, and omitted assert.expect(N). The skill-guided output used async/await, nextUIUpdate, const, and assert.expect(2) — production-ready out of the box.

Eval 2 — modernizing an existing ToggleButton test from openui5: Both outputs did a solid job (const/let, beforeEach/afterEach, destroy). The skill added one meaningful extra: it caught that the file used the deprecated sap/ui/qunit/utils/nextUIUpdate import path and corrected it to sap/ui/test/utils/nextUIUpdate. The baseline missed this.

Eval 3 — QUnit 1 → QUnit 2 migration guide (8/8 vs 5/8): Both covered the core QUnit 2 API changes. The skill additionally covered replacing Core.applyChanges() with nextUIUpdate() including the fake-timer exception (nextUIUpdate(this.clock)) — entirely absent in the baseline.

The gap identified during eval (the sap.ui.getCore() import rule from modernizing-tests.md not being reflected in SKILL.md) has been fixed in this PR as part of the same iteration.

The so called gap is not really relevant, as it's already implemented in the subsidiary files.

Also recommended by @kineticjs , I ran this skill guideline.

Here is the AI summary of it:

1. Description is not third-person
The guide says descriptions must be third person ("Processes Excel files..." not "Use when the user..."). The current description starts with Use when the user asks to... — that's instructional, not third-person. It should read like: "Covers coding standards for OpenUI5/SAPUI5 QUnit test files... Use when writing, modernizing or migrating QUnit tests..."

2. Description mixes "what" and "when" awkwardly
The guide recommends: what it does first, then "Use when..." triggers. Currently it leads with triggers and buries the "what" at the end.

3. No table of contents in the longer reference files
The guide recommends a ToC at the top of any reference file over 100 lines so Claude can navigate it efficiently. modernizing-tests.md and writing-new-tests.md are both well over 100 lines with no ToC.

4. The async-patterns.md reference isn't surfaced clearly enough
The guide recommends the SKILL.md routing table be the primary navigation aid — currently the table does point to it, but only for "any test touches nextUIUpdate". That file is relevant more broadly.

Want me to fix all four of these? The description rewrite is the highest-value one — it directly affects whether the skill triggers reliably.

Basically it's more polish than actual relevant changes. AI recommends leaving the current PR as is, being relevant and useful.