docs on data providers don't say provided values can't be anonymous functions

[joachim-n]

Trying to use an anonymous function as a value in a data provider crashes phpunit.

The docs should say what the limitations are on possible data provider values.

[sebastianbergmann]

It never occurred to me that one would use anonymous functions as "values" in data providers. That being said, AFAICS it seems to work:

<?php declare(strict_types=1);
namespace PHPUnit\TestFixture;

use PHPUnit\Framework\Attributes\DataProvider;
use PHPUnit\Framework\TestCase;

final class DataProviderAnonymousFunctionTest extends TestCase
{
    public static function provider(): array
    {
        return [
            [function () { return true; }],
        ];
    }

    #[DataProvider('provider')]
    public function testOne(callable $a): void
    {
        $this->assertIsCallable($a);
        $this->assertTrue($a());
    }
}

[joachim-n]

I get:

Message: Serialization of 'Closure' is not allowed
Location: /var/www/html/vendor/phpunit/phpunit/src/Framework/TestRunner.php:306

But that's on PHPUnit 10.5.20.

Good to know this is supported in 11.

The use case was tests that do nearly everything the same except a few additional steps of setup -- details here https://www.drupal.org/project/drupal/issues/3278083#comment-15666084