Add unit tests for wp_refresh_heartbeat_nonces() in wp-admin/includes…

[pbearne]

…/misc.php
Description:
This PR adds unit tests for the wp_refresh_heartbeat_nonces() function in wp-admin/includes/misc.php. This function is responsible for adding refreshed REST API and Heartbeat nonces to the response sent back during Heartbeat requests.

The tests cover:

• Successful addition of rest_nonce and heartbeat_nonce to an existing response array.
• Verification that existing data in the response is preserved.
• Verification that if the nonces already exist in the response, they are correctly overwritten with new, valid nonces.

Trac ticket: https://core.trac.wordpress.org/ticket/65199

AI Disclosure:

• AI assistance: Yes
• Tool(s): Junie (JetBrains)
• Model(s): gemini-3-flash-preview
• Used for: Code analysis, test implementation, and workflow management.

[github-actions]

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Unlinked Accounts

The following contributors have not linked their GitHub and WordPress.org accounts: @pbearne@git.wordpress.org.

Contributors, please read how to link your accounts to ensure your work is properly credited in WordPress releases.

To understand the WordPress project's expectations around crediting contributors, please review the Contributor Attribution page in the Core Handbook.

[github-actions]

Test using WordPress Playground

The changes in this pull request can previewed and tested using a WordPress Playground instance.

WordPress Playground is an experimental project that creates a full WordPress instance entirely within the browser.

Some things to be aware of

• All changes will be lost when closing a tab with a Playground instance.
• All changes will be lost when refreshing the page.
• A fresh instance is created each time the link below is clicked.
• Every time this pull request is updated, a new ZIP file containing all changes is created. If changes are not reflected in the Playground instance,
  it's possible that the most recent build failed, or has not completed. Check the list of workflow runs to be sure.

For more details about these limitations and more, check out the Limitations page in the WordPress Playground documentation.

Test this pull request with WordPress Playground.

[github-actions]

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 62356
GitHub commit: 83d68ce

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.