[13.x] artisan test --parallel broken with PHPUnit 13.4: PhpHandler requires Emitter #61857

Laravel Version

13.34.0

PHP Version

8.4.26

Database Driver & Version

MySQL 8 (not relevant)

Description

PHPUnit 13.4.0 (released 2026-10-02) changed the constructor of PHPUnit\TextUI\Configuration\PhpHandler, which now requires a PHPUnit\Event\Emitter argument:

public function __construct(Emitter $emitter)

Illuminate\Testing\Concerns\RunsInParallel still instantiates it without arguments (line 110, same on 13.x and master):

(new PhpHandler())->handle($configuration->php());

As a result, php artisan test --parallel fails immediately with an ArgumentCountError as soon as phpunit/phpunit 13.4.0 is installed. Non-parallel runs are not affected.

PHPUnit itself now calls it as new PhpHandler($this->emitter) (src/TextUI/Application.php). A possible fix keeping compatibility with PHPUnit < 13.4 would be to pass PHPUnit\Event\Facade::emitter() when the constructor has a required parameter.

Other versions: nunomaduro/collision 8.9.5, brianium/paratest 7.25.0.

Workaround for now: pin "phpunit/phpunit": "~13.3.6".

Steps To Reproduce

1. Fresh Laravel 13.34.0 app with phpunit/phpunit 13.4.0 and brianium/paratest.
2. Run php artisan test --parallel.
3. ArgumentCountError: Too few arguments to function PHPUnit\TextUI\Configuration\PhpHandler::__construct(), 0 passed.