Clinner\Command\Tests\CallbackTest::testGetErrorOutput PHP Method

    public function testGetErrorOutput()
    {
        $closure = function () {
            echo 'Do nothing';
        };
        $callback = new Callback($closure);
        // Output must be null before the command is run
        $this->assertNull($callback->getErrorOutput());
        $callback->run();
        // Output must remain null after the command is run with the given $closure
        $this->assertNull($callback->getErrorOutput());
    }