Test tool and unit test improvements for 7.2

[desrosj]

This ticket is for various fixes and improvements in PHPUnit tests that don't have a more specific ticket, as well as general improvements to the GitHub Actions workflows that run automated testing.

Previous releases:

• #64894 (7.1)
• #64225 (7.0)
• #63167 (6.9)
• #62280 (6.8)
• #61530 (6.7)
• #60705 (6.6)
• #59647 (6.5)
• #58955 (6.4)
• #57841 (6.3)
• #56793 (6.2)
• #55652 (6.1)
• #54725 (6.0)
• #53363 (5.9)
• #52625 (5.8)
• #51802 (5.7)
• #51344 (5.6)

This removes some PHPUnit back-compat that's no longer needed.

• PHPUnit 6 hasn't been used since ​support for PHP 7.0 and 7.1 was dropped in WordPress 6.6.
• PHPUnit 8 is no longer used since ​support for PHP 7.2 and 7.3 was dropped in WordPress 7.0.

This leaves PHPUnit 9 as the only version currently in use.

Trac ticket:
https://core.trac.wordpress.org/ticket/65819
https://core.trac.wordpress.org/ticket/64894

## Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Opus 4.7
Used for: Initial investigation and changes, with follow-ups and fixes by me.

## Description

remove_filter( $hook_name, $callback, $priority = 10 ) and remove_action( $hook_name, $callback, $priority = 10 ) take three parameters. A number of places in the PHPUnit test suite pass a fourth one, copied over from the matching add_filter()/add_action() call:

add_filter( 'domain_exists', array( $this, 'domain_exists_cb' ), 10, 4 );
$exists = domain_exists( 'foo', 'bar' );
remove_filter( 'domain_exists', array( $this, 'domain_exists_cb' ), 10, 4 );

The fourth argument is silently ignored by PHP, but it is misleading: it suggests $accepted_args is part of the callback identity used to locate and unhook the callback, which it is not. Only the hook name, the callback and the priority are relevant.

This removes the superfluous argument throughout the test suite. Where the priority was the default 10, the now-redundant priority argument is dropped as well:

remove_filter( 'domain_exists', array( $this, 'domain_exists_cb' ) );

Non-default priorities are kept, since remove_filter() only finds a callback under the exact priority it was registered with:

remove_filter( 'pre_do_shortcode_tag', array( $this, 'filter_pre_do_shortcode_tag_attr' ), 12 );

No occurrences remain in src/, so this is a test-only change with no behavioural difference.

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

Replaces six generic assertTrue( is_callable() ) assertions in
tests/phpunit/tests/customize/widgets.php with PHPUnit's dedicated
assertIsCallable() assertion.

This is a test-only cleanup and does not change WordPress runtime behavior.

## Testing

• npm run test:php -- --filter Tests_WP_Customize_Widgets::test_get_setting_args --colors=never --do-not-cache-result
  • PASS: 1 test, 43 assertions

• npm run test:php -- --filter Tests_WP_Customize_Widgets --colors=never --do-not-cache-result
  • PASS: 28 tests, 410 assertions

Current upstream verification also confirmed that the target file has not
changed since the candidate parent and that the six legacy assertions remain
present on current trunk.

## Use of AI Tools

AI assistance: Yes
Tool(s): ChatGPT
Model(s): GPT-5.6 Sol
Used for: Investigation support, contribution workflow and validation
planning, and drafting assistance. The change was reviewed, understood,
signed, and tested by me.

---
This Pull Request is for code review only. Please keep all other
discussion in the Trac ticket. Do not merge this Pull Request. See
​GitHub Pull Requests for Code Review
in the Core Handbook for more details.

We have the same pattern in Tests_Multisite_WpCacheSwitchToBlogFallback:

​https://github.com/WordPress/wordpress-develop/blob/ef4d2ff2c252e0b1c4841392ec359757e5c5e05a/tests/phpunit/tests/multisite/wpCacheSwitchToBlogFallback.php#L124-L125

Thanks — I've added those two occurrences in
Tests_Multisite_WpCacheSwitchToBlogFallback as a focused follow-up.

The additional change is limited to that one file (+2/-2), replacing the
two assertTrue( is_callable() ) assertions with assertIsCallable().

Fresh validation passes:

• targeted multisite method: 1 test, 4 assertions
• full multisite class: 25 tests, 136 assertions
• existing Customize class: 28 tests, 410 assertions
• PHP coding standards: PASS

## Description
Four independent clean-ups in the test file. Follow-up to [60906].

• Remove the unused $user_ids fixture. The property and its wpSetUpBeforeClass() method were copied over from the wp_insert_post() tests. Nothing in this class references self::$user_ids, so the only effect was creating three users for every test in the class.
• Rename test_wp_delete_post_returns_false_for_invalid_post() to test_wp_delete_post_returns_null_for_already_deleted_post(). The test asserts assertNull(), and that is the correct expectation: for an ID with no matching row, wp_delete_post() returns the null coming out of $wpdb->get_row(), whereas false is only returned by the $post_id <= 0 guard. The old name described the opposite of what the test covers.
• Reuse the $actions array in the assertion loop of test_wp_delete_post_actions(). The same six action names were spelled out a second time inline, so the registration loop and the assertion loop could drift apart.
• Fix the @ticket @63975 annotation. The stray @ made the tag invalid, so the test was not associated with the ticket.

No assertion was added, removed or changed, and no test behaviour changes.

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

[SergeyBiryukov]

In 63295:

Tests: Clean up the wp_delete_post() unit tests.

Four independent clean-ups in the test file:

• Remove the unused $user_ids fixture. The property and its wpSetUpBeforeClass() method were copied over from the wp_insert_post() tests. Nothing in this class references self::$user_ids, so the only effect was creating three users for every test in the class.
• Rename test_wp_delete_post_returns_false_for_invalid_post() to test_wp_delete_post_returns_null_for_already_deleted_post(). The test asserts assertNull(), and that is the correct expectation: for an ID with no matching row, wp_delete_post() returns the null coming out of $wpdb->get_row(), whereas false is only returned by the $post_id <= 0 guard. The old name described the opposite of what the test covers.
• Reuse the $actions array in the assertion loop of test_wp_delete_post_actions(). The same six action names were spelled out a second time inline, so the registration loop and the assertion loop could drift apart.
• Fix the @ticket @63975 annotation. The stray @ made the tag invalid, so the test was not associated with the ticket.

No assertion was added, removed or changed, and no test behavior changes.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/13036.

Follow-up to [60906].

Props Soean.
See #65819.

Committed in ​https://github.com/WordPress/wordpress-develop/commit/5a96e2aa643fe20218267026ebfa2ea6cc63e161

Two test cases still used the legacy PHPUnit stub API. This replaces them with the modern shorthands, which are what the rest of the suite already uses.

### Description

tests/phpunit/tests/pomo/pluralForms.php

// Before
->will( $this->returnValue( 1 ) );
// After
->willReturn( 1 );

tests/phpunit/tests/rest-api/rest-server.php

// Before
->with( $this->equalTo( 400 ) );
// After
->with( 400 );

### Why this is safe

willReturn() is a direct shorthand for will( $this->returnValue() ) and has been available since PHPUnit 5.4. The test suite enforces a minimum of PHPUnit 5.7.21 in tests/phpunit/includes/bootstrap.php, so it is safe on every supported version, and the suite already contains 83 willReturn() calls.

with() wraps any non-Constraint argument in an equalTo() constraint itself, so passing 400 directly is identical in behaviour. The suite already has 43 with() calls that pass values directly.

Note on the first change: that line was originally written as willReturn( 1 ) and switched to the long form in [41725] because of the PHPUnit versions supported back then. That constraint no longer applies, so this effectively reverts an obsolete workaround.

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

[SergeyBiryukov]

In 63303:

Tests: Use the modern PHPUnit stubbing and matcher shorthands.

Two test cases still used the legacy PHPUnit stub API. This replaces them with the modern shorthands, which are what the rest of the suite already uses.

tests/phpunit/tests/pomo/pluralForms.php

// Before
->will( $this->returnValue( 1 ) );
// After
->willReturn( 1 );

tests/phpunit/tests/rest-api/rest-server.php

// Before
->with( $this->equalTo( 400 ) );
// After
->with( 400 );

Why this is safe

willReturn() is a direct shorthand for will( $this->returnValue() ) and has been available since PHPUnit 5.4. The test suite enforces a minimum of PHPUnit 5.7.21 in tests/phpunit/includes/bootstrap.php, so it is safe on every supported version, and the suite already contains 83 willReturn() calls.

with() wraps any non-Constraint argument in an equalTo() constraint itself, so passing 400 directly is identical in behaviour. The suite already has 43 with() calls that pass values directly.

Note on the first change: that line was originally written as willReturn( 1 ) and switched to the long form in r41725 because of the PHPUnit versions supported back then. That constraint no longer applies, so this effectively reverts an obsolete workaround.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/13052.

Follow-up to r34928, r41725.

Props Soean.
See #65819.

Committed at https://core.trac.wordpress.org/changeset/63303

[SergeyBiryukov]

In 63311:

Tests: Use assertIsCallable() for callable assertions.

Replaces eight generic assertTrue( is_callable() ) assertions with PHPUnit's dedicated assertIsCallable() assertion.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/13017.

Follow-up to r50996, r61760.

Props raulsalvat, Soean.
See #65819.

Committed at https://core.trac.wordpress.org/changeset/63311

PHP 8.6 is due out at the end of 2026. ​Beta 1 was released on August 13th.

This adds a PHP 8.6 job to the PHPUnit testing matrix, but configures jobs using that version to be allowed to fail.

Trac ticket: Core-65819.

## Use of AI Tools
None

I'm not sure that we need to be testing with every DB provider for the time being. What would you think of excluding some of the combinations from the matrix?

Tests_Theme::test_get_theme() wraps a native type check in a boolean assertion. PHPUnit has a dedicated assertion for this, which states the intent directly and reports a more useful message when it fails. The comment above it is reworded in the same change, as it referred to the is_array() call that is no longer there.

This is the last remaining convertible occurrence in the test suite.

Follow-up to [62761], [63311].

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

[SergeyBiryukov]

In 63401:

Tests: Use assertIsNotArray() for array type assertions.

Tests_Theme::test_get_theme() wraps a native type check in a boolean assertion. PHPUnit has a dedicated assertion for this, which states the intent directly and reports a more useful message when it fails. The comment above it is reworded for clarity.

Developed in ​https://github.com/WordPress/wordpress-develop/pull/13305.

Follow-up to r62761, r63311.

Props Soean, mukesh27, SergeyBiryukov.
See #65819.

Thanks for the PR! Merged in r63401.

I've mostly reverted my original changes in favor of creating a new job solely for PHP 8.6. This makes it much easier to manage the number of combinations and the values passed to the various inputs for the reusable workflow without needing to add a bunch of conditional checks.

We could pare it back further if we'd like. I chose to go with one multisite and one single site job on both the latest LTS version of MySQL and MariaDB. It adds 4, but I think that's reasonable to get feedback while running the latest versions of both projects that WordPress currently recommends to users.

Looks good to land. We can adjust from there.