please clarify if this problem is also present in runSymfonyConsoleCommand, because when reading it seems to be exclusive of runShellCommand.

I'm not sure if I tried. But the mail assertions are working by looking at the web debug toolbar, aren't they?

I didn't try runSymfonyConsoleCommand(). Is there a way to pipe input to the command?
Right now, I'm doing:

$I->runShellCommand('printf "foobar" | php bin/console app:my_command --env=test');

@ThomasLandauer yes, you can use the third parameter $consoleInputs for that. So the equivalent to the above would be

$I->runSymfonyConsoleCommand('app:my_command', ['--env' => 'test'], ['foobar']);

Hm, then the test executions hangs at this line - looks like the console is waiting for something. I didn't look into it further - are you sure that this works?

@ThomasLandauer I tested it before writing that comment just to be sure, so yes, it does work in general. Maybe we're talking about different things, so I created Codeception/symfony-module-tests#28 to demonstrate what I'm talking about.

The test is a cool idea!
My command doesn't ask questions (i.e. doesn't wait for input), it reads input from STDIN:

$fread = fread(STDIN, $length);

@ThomasLandauer oh, I see. I didn't have such a use case yet, so I don't know, but the console input parameter might indeed not work with STDIN then.

is not clear why it is more 'professional'.

Please explain what Mailpit is and how it works as an alternative to what within Codeception exactly, in what specific scenario you are going to recommend its use and how to integrate it into the functional testing workflow with this module.

by the way, there is a tiny typo in 'wchich'.

I'm not sure if I tried. But the mail assertions are working by looking at the web debug toolbar, aren't they?

Please merge Codeception/codeception.github.com#880 first, so I can add a link to it here. I don't think adding all features of Mailpit here is a good idea, cause nobody will ever update that :-)
IMO the main advantage is that you can assert the mail's content. And sooner or later most people probably want a mailcatching solution anyway (not just for testing, but also for development), so I'm figuring it's a good idea to tell them early...

I didn't try runSymfonyConsoleCommand(). Is there a way to pipe input to the command?
Right now, I'm doing:

$I->runShellCommand('printf "foobar" | php bin/console app:my_command --env=test');