Summary

If the SUT forks a child process and waits for it to exit, the test will output "Fatal error: Premature end of PHP process".

Current behavior

The test passes but outputs an error message. Interestingly beStrictAboutOutputDuringTests="true" has no effect here.

How to reproduce

final readonly class Forker
{
    public function fork(): bool
    {
        $child = pcntl_fork();

        if ($child === -1) {
            // couldn't fork
            return false;
        } elseif ($child) {
            // we are the parent process
            pcntl_wait($child);
            return true;
        } else {
            // we are the child process
            exit(0);
        }
    }
}

final class ForkerTest extends TestCase
{
    public function testFork(): void
    {
        $actual = (new Forker())->fork();
        self::assertTrue($actual);
    }
}

Output:

✗ vendor/bin/phpunit test/ForkerTest.php 
PHPUnit 12.4.2 by Sebastian Bergmann and contributors.

Runtime:       PHP 8.3.27
Configuration: /Users/xxx/yyy/phpunit.xml

Fatal error: Premature end of PHP process when running ForkerTest::testFork.
.                                                                   1 / 1 (100%)

Time: 00:00.013, Memory: 20.00 MB

OK (1 test, 1 assertion)

(In the real world I'm testing Swoole stuff, which is a headache enough 😁 )

Expected behavior

I'm not sure if anything can be done with ShutdownHandler that would detect if it were in a child process. If not, it would be good to have a way to suppress the message. Right now I'm calling ShutdownHandler::resetMessage(), but that method is @internal.