[8.x] Added a 'expectedOutputNever' method for console command testing

[ash-jc-allen]

Hi!

This pull request adds a new ->expectsOutputNever() method can be used for testing console commands. I think that this could be quite useful for helping to make the console tests a bit stricter.

This might not be the best example to show where it could be used, but it should hopefully give you a bit of an idea:

Command:

public function handle()
{
    if ($this->something()) {
        $this->info('Something is truthy!');
    }

    // Continue the rest of the command...

    return 0;
}

Test:

public function test_the_command_when_something_is_falsey()
{
    $this->artisan('signature')
        ->expectsOutputNever('Something is truthy!')
        ->assertExitCode(0);
}

public function test_the_command_when_something_is_truthy()
{
    $this->artisan('signature')
        ->expectsOutput('Something is truthy!')
        ->assertExitCode(0);
}

I'm hoping that you all think it could be valuable and would help with writing console tests. If I've targeted this to the wrong branch or if it needs any changes if you want to pull it in, please let me know and I'll update it straight away. 😄

[taylorotwell]

Does not work with two Artisan commands in one test.

[ash-jc-allen]

Ah okay, I completely forgot to try with more than 1 command in a test. I'll take another look and update it

[taylorotwell]

I'll fix it.

[taylorotwell]

Renamed to doesntExpectOutput.