Please explain the router code.

The last `str_replace()` is not covered by PHPUnit tests.
RouterTest passes if I remove the line.

PHP Code:

$routeKey: api/posts/(.*)
$replacekey: api/posts
$handler: \App\Controllers\Api\PostController::show/50
$handler: \App\Controllers\Api\PostController::show/50 


PHP Code:

$routeKey: api/posts/(.*)/edit
$replacekey: api/posts/edit
$handler: \App\Controllers\Api\PostController::edit/50
$handler: \App\Controllers\Api\PostController::edit/50 


PHP Code:

$routeKey: api/posts/(.*)
$replacekey: api/posts
$handler: \App\Controllers\Api\PostController::update/50
$handler: \App\Controllers\Api\PostController::update/50 


---

It seems the code came from https://github.com/codeigniter4/CodeIgniter4/pull/344

ci-phpunit-test | CodeIgniter Testing Guide | CodeIgniter 3 to 4 Upgrade Helper