--process-isolation causes "Test was run in child process and ended unexpectedly"

[calbro7]

Q	A
PHPUnit version	9.6.15
PHP version	8.3.10
Installation Method	Composer

Summary

Running with --process-isolation does not show the proper outcome of a failed test when the trace involves a closure, it displays the message "Test was run in child process and ended unexpectedly".

Current behavior

As above.

How to reproduce

Run the following:

<?php

namespace App\Tests;

use PHPUnit\Framework\TestCase;

class ExampleTest extends TestCase
{
	public static function assertClosureReturnsValue(\Closure $closure, mixed $value): void
	{
		static::assertEquals($value, $closure());
	}

	public function testExample(): void
	{
        static::assertClosureReturnsValue(fn () => 1, 2);
	}
}

with phpunit --filter=ExampleTest --process-isolation

and see the outcome:

Expected behavior

It should produce the same outcome as running without --process-isolation: