[huzaifaalmesbah]

Description

Adds tests for validate_active_plugins(), which deactivates active plugins that are missing or invalid when the Plugins screen loads, and for the validate_plugin() errors it reports. The existing tests only check a removed plugin being reported and the empty case.

The tests use a temporary plugin file without a header and the plugins in the test data directory. They cover:

• an active_plugins option that is not an array (a string or an integer) being reset;
• valid active plugins being kept;
• the plugin_invalid, plugin_not_found and no_plugin_header errors with their messages, and the invalid plugins being deactivated silently while the valid one stays active;
• on multisite, network-active plugins being validated and deactivated for a user who can manage network plugins, and left alone for other users.

Removing or changing each branch of the two functions makes at least one test fail on single site or multisite.

This is a test-only change; no production code is modified.

Testing Instructions

1. Run the tests on single site:
   npm run test:php -- --filter Tests_Admin_Includes_Plugin_ValidateActivePlugins
2. Run them on multisite:
   npm run test:php -- --filter Tests_Admin_Includes_Plugin_ValidateActivePlugins -c tests/phpunit/multisite.xml
3. Run them in random order:
   npm run test:php -- --filter Tests_Admin_Includes_Plugin_ValidateActivePlugins --order-by=random
4. Run the plugins group:
   npm run test:php -- --group plugins
5. Run PHPCS on the test file:
   node ./tools/local-env/scripts/docker.js run --rm php ./vendor/bin/phpcs tests/phpunit/tests/admin/includes/plugin/validateActivePlugins.php

Trac ticket: https://core.trac.wordpress.org/ticket/65819

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5.5
Used for: Brainstorming edge-case scenarios and drafting test boilerplate; test architecture, assertions, and local PHPUnit verification were written and validated by me.

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Props huzaifaalmesbah, mukesh27.

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[mukeshpanchal27]

The assertions match the source, and CI passes. One note about fixture cleanup inline.

[mukeshpanchal27]

In core tests, WP_PLUGIN_DIR is tests/phpunit/data/plugins, which is a tracked directory. If a run stops partway, such as on a fatal error or Ctrl+C, tear_down() never runs and this fixture folder stays there. The folder name is fixed, so this assertion fails on the next run. So every test in the class fails here until someone deletes the folder by hand. The leftover also shows up in git status.

Could this helper, or set_up(), remove a leftover folder first? #14600 already does this: its remove_plugin() helper runs in both set_up() and tear_down().

[huzaifaalmesbah]

Good catch, thanks! Added a remove_plugin() helper that runs in both set_up() and tear_down(), in 7d99d5d. I checked it with a leftover folder in place: the old code failed and the new code passes.