PHPUnit test freezes when testing ChoiceCommand with multiSelect enabled

[dugajean]

Symfony version(s) affected: Console 4.2.3

Description
This is a standalone Symfony Console project. I have one simple test, to test a command that requires input. I use the setInputs method in the test on $commandTester and input 6 answers there for the 6 questions that will be asked. However, the test hangs at the ChoiceQuestion with multiSelect enabled ($question->setMultiselect(true);), causing PHP to use a lot of processing power (CPU usage) and the Terminal ends up using a lot of RAM.

How to reproduce
Make a simple test like this one:

<?php

namespace Dockr\Tests\Command;

use MyApp\Commands\MyCoolCommand;
use Symfony\Component\Console\Application;
use Symfony\Component\Console\Tester\CommandTester;

class MyCoolCommandTest extends TestCase
{
    public function testExecute()
    {
        $application = new Application();
        $application->add(new MyCoolCommand);

        $command = $application->find('do_cool_stuff');

        $commandTester = new CommandTester($command);
        $commandTester->setInputs(['This', 'This', 'This', 'This', 'This', 'This']);
        $commandTester->execute(['command' => $command->getName()]);
    }
}

And make sure that there is one multiSelect question ($question->setMultiselect(true);). The question should hang at the $questionHelper->ask($input, $output, $question) call.

Please note: This command works perfectly fine when running the command manually, only fails when running it via a test like above.

[chalasr]

I confirm it hangs when no input is given to the question (that is a bug).
However, it works as expected if you set the proper inputs.
Can you show the tested command? Note that, as in a regular cli context, a multi-select input must be only one string with coma-separated values, i.e:

// command
$question = new ChoiceQuestion('Choice', ['a', 'b', 'c']);
$questionHelper->ask($input, $output, $question);

// test
$tester->setInputs('a, b');

And if your command asks multiple questions, an input string must be set for all of them (using an empty string for simulating enter).
I'm looking at fixing the issue when one or more inputs are missing.

[dugajean]

Good! Thank you!

Well, I provided wrong input - input that wasn't part of the $choices. That resulted in a hang as well.

Yes, I'm aware that you need to provide an answer for each question. Above you can see 6 answers (This x 6) for my 6 questions in the command. I will provide the command later today.

[chalasr]

Providing a wrong input to a choice question leads to the question being asked again, except if the question has no validator or if $question->setMaxAttempts(1) has been called, hence it behaves as a missing input (since no input is set for the second attempt).
Still, tests should never hang. #30271 fixes it, would be nice to have your confirmation.

[dugajean]

@chalasr The test passes now. Thanks a lot!