Fix: clean up registered theme directories and theme cache in teardown - #896

What?

Closes #895

Fixes a test isolation failure where CbtThemeLocale and CbtThemeReadme test suites leak custom theme directory registrations into the global $wp_theme_directories array and leave stale theme caches, causing 1 error and 5 failures in subsequent test classes (Test_Create_Block_Theme_Api and Test_Create_Block_Theme_Fonts).

Why?

CBT_Theme_Locale_UnitTestCase and CBT_Theme_Readme_UnitTestCase register DIR_TESTDATA . '/themes/' via register_theme_directory() during set_up(). In tear_down(), they switch back to the original theme, but never remove the registered directory from $wp_theme_directories and never call wp_clean_themes_cache().

This leaves registered theme directories leaked in the global $wp_theme_directories array and theme caches stale across the test suite. Subsequent tests that dynamically create themes on disk (such as Test_Create_Block_Theme_Api and Test_Create_Block_Theme_Fonts) fail to resolve them properly, leading to test failures during full suite runs.

How?

• tests/CbtThemeLocale/base.php:
  • Captured the original $wp_theme_directories in set_up().
  • Restored $wp_theme_directories to its original state and called wp_clean_themes_cache() in tear_down().
• tests/CbtThemeReadme/base.php:
  • Captured the original $wp_theme_directories in set_up().
  • Restored $wp_theme_directories to its original state and called wp_clean_themes_cache() in tear_down().

Testing Instructions

1. Run CBT_Theme_Locale_EscapeAttribute immediately followed by Test_Create_Block_Theme_Api:

   npm run test:unit:php:base -- --filter "CBT_Theme_Locale_EscapeAttribute|Test_Create_Block_Theme_Api"

   Verify that all 19 tests pass without failures.
2. Run the full unit test suite:

   npm run test:unit:php:base

   Verify that all 273 tests run cleanly with 0 errors and 0 failures.

Use of AI Tools

AI assistance: Yes
Tool(s): Antigravity
Model(s): Gemini
Used for: Diagnosing test pollution root cause in WordPress Core theme lookup and implementing test teardown cleanup. Final decisions and edits were made by me.