CC integration: Unit test rules

[stracker-phil]

Description

Adds Claude Code developer tooling to standardize PHP unit test writing across the project.

What's included

• .claude/agents/unit-test-writer.md: A sub-agent with instructions for writing PHPUnit tests in this codebase. It includes:
  • GIVEN/WHEN/THEN doc blocks on every test method
  • A general naming convention
  • Stub-over-mock preference, with a decision table to justify mocks
  • Data providers with descriptive string keys
  • Required patterns: stateful fixture closures, testable subclasses for protected methods
  • A quality checklist the agent must verify before delivering
  • Relevant DDEV test commands
• .claude/rules/unit-test-conventions.md: A Claude Code rule scoped to tests/PHPUnit/**/*.php that instructs the assistant to always delegate test writing to the new unit-test-writer agent, never inline.
• .gitignore update: Adds general support to track relevant claude code files (include all .claude/ content, but exclude all *.local.* files in all folders).

Why

Test quality has been inconsistent - missing doc blocks, mocks where stubs suffice, no data providers, tests asserting implementation details. Routing all test work through a specialized agent with hard-wired conventions prevents regressions in test quality without requiring manual review of every test PR.

Samples

Test files created by this agent:

• https://github.com/woocommerce/woocommerce-paypal-payments/blob/12c23b7dfc32d177509b690b5ece0f1d360c9a9b/tests/PHPUnit/StoreSync/Auth/PayPalJwkProviderTest.php
• https://github.com/woocommerce/woocommerce-paypal-payments/blob/85bd336a146273430f23793d07f96a82514857e5/tests/PHPUnit/StoreSync/Helper/AgenticCheckoutProcessorTest.php
• https://github.com/woocommerce/woocommerce-paypal-payments/blob/12c23b7dfc32d177509b690b5ece0f1d360c9a9b/tests/PHPUnit/StoreSync/Helper/PayPalOrderManagerTest.php

[github-actions]

Test using WordPress Playground

The changes in this pull request can be previewed and tested using a WordPress Playground instance.
WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

🔗 Test this pull request with WordPress Playground

What's included:

• ✅ WordPress (latest)
• ✅ WooCommerce (latest)
• ✅ PayPal Payments plugin v4.1.1-pr4323-29851033239-gba2d8cb (built from this PR)

Login credentials:

• Username: admin
• Password: password

Plugin Details:

• Version: 4.1.1-pr4323-29851033239-gba2d8cb
• Commit: b9d735e
• Artifact: woocommerce-paypal-payments-4.1.1-pr4323-29851033239-gba2d8cb

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_{🤖 Auto-generated for commit b9d735e • Last updated: 2026-07-21T17:04:47.382Z}