Run the development build during prepare

[ekamran]

Fixes #350.

Problem

Since core r63983, host reports fail four tests: Tests_Dependencies_jQuery::test_jquery_files_exist for jquery.js, jquery.min.js, jquery-migrate.js and jquery-migrate.min.js.

On the results site, r63982 has 22 passed and 2 failed reports. r63983 has 3 passed and 27 failed, and r64091 is still at 3 and 24. Only core's own reporter passes.

prepare.php runs npm run build, which writes the built files to build/. The test suite runs against src/, which is ABSPATH in the generated wp-tests-config.php. The new test asserts that the jQuery files exist under src/wp-includes/js/jquery/, and only the development build creates that directory.

Fix

Run npm run build:dev instead. It writes the built files into src/, and it is the build that core's own PHPUnit workflow runs: npm ci, then npm run build:dev.

What changes for hosts

• The four jQuery tests pass.
• Tests_Basic::test_build_wp_version_does_not_end_with_src is now skipped, because build/ is no longer produced. Core's own workflow skips it for the same reason.
• Prepare gets a little lighter. There is no build/ directory, which was 152 MB in my run.

Verification

Real end to end runs of prepare.php and test.php against trunk r64092, PHP 8.5, MySQL 9.7.

• master: src/wp-includes/js/jquery/ does not exist after prepare, and the four tests fail with the same messages as in host-tests failing since r63983 (missing/invalid jQuery paths?) #350.
• This branch: the four files exist in src/, and Tests_Dependencies_jQuery passes with 7 tests and 48 assertions.
• Same comparison across the groups most likely to care about built files (dependencies, scripts, blocks, restapi, and the five test files that reference built paths, about 4,800 tests): the only differences are the four fixed tests and the one skipped test above.
• Full suite, 25,703 tests: master ends with 4 failures, the same four tests, and 73 skipped. This branch ends with no failures and 74 skipped. The extra skip is the build version test above.
• php -l, phpcs and git diff --check are clean.

Notes

• This touches the same line as Run npm verbosely when debug mode is enabled #340, which adds the verbosity flags to both npm commands. Whichever lands second needs a one-line rebase, and I will do it.
• Document why NodeJS is needed to run the tests #347 adds README text that names npm run build. It would need the same one-word update.
• The runner's own checks did not catch this because the test step runs with continue-on-error. That is outside this PR.

Use of AI

AI assistance: Yes
Tool(s): Claude Code and Codex
Used for: Investigation, implementation, verification harness, and PR wording. I reviewed the reasoning and test results, and I take responsibility for the contribution.

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Co-authored-by: ekamran <ekamran@git.wordpress.org>
Co-authored-by: kittenkamala <amykamala@git.wordpress.org>
Co-authored-by: kmott <mywp459@git.wordpress.org>

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[kittenkamala]

Thank you so much for catching this. Would be great to have some hosts test on their systems to confirm the change to using build:dev is effective.

Maybe @jazzsequence and @chrisdavidmiles could test on Pantheon and BlueHost systems