protected function addHelpValue($key, $value)
    {
        if (is_object($value)) {
            throw new \InvalidArgumentException(sprintf('The HelpValue with ID "%s" you are trying to add is an object. Use $this->addHelpMock() instead.', $key));
        }

        if (isset($this->helpValues[$key])) {
            throw new \LogicException('The HelpValue you are trying to add is already set. Set the fourth parameter to "true" to overwrite it.');
        }

        $this->helpValues[$key] = $value;

        return $this;
    }