Tests: Add coverage for _wp_rest_get_debug_backtrace_caller().

[rvpatel]

Hi @ilclaudio! This adds PHPUnit coverage for the new _wp_rest_get_debug_backtrace_caller() helper in your PR WordPress#10537, so it can be merged straight into your branch. It only adds one test file and does not change your code.

Trac ticket: https://core.trac.wordpress.org/ticket/64260

What is covered

tests/phpunit/tests/rest-api/wpRestGetDebugBacktraceCaller.php, 8 tests:

• A call from a named function reports called from func() in /path on line N.
• Instance and static methods report Class->method() and Class::method().
• A closure is reported as (anonymous function).
• A call from a file's global scope reports only the location, not require/include.
• The innermost frame inside WP_CONTENT_DIR is reported when several are.
• A call from outside WP_CONTENT_DIR returns an empty string.
• A sibling directory such as wp-content-backup is not treated as part of wp-content (the trailingslashit() fix from review).

Each test calls the helper from a fixture file written inside WP_CONTENT_DIR, the way a plugin would, and removes it afterwards.

Testing

npm run test:php -- tests/phpunit/tests/rest-api/wpRestGetDebugBacktraceCaller.php

• All 8 tests pass on your branch (head 0f1ef94359). PHPCS is clean.
• To check they catch regressions, I broke the helper four ways and the tests failed each time: removing trailingslashit(), the closure label, the include/require check, and the class prefix.
• The restapi group has the same failures with and without this file, so it does not affect other tests.

The error_log() lines in the three handlers are not covered: the test suite does not define WP_DEBUG_LOG, so it is always false there and that path cannot be reached without a separate process.

Use of AI Tools

AI assistance: Yes
Tool(s): Claude Code
Model(s): Claude Opus 5.5
Used for: Drafting the test cases and running the checks. I reviewed the tests and the results.

[github-actions]

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Props ravipatel.

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[ilclaudio]

Merge done