public function addData($mixedData)
    {
        if (false === isset($this->cases[$this->currentCaseTitle])) {
            throw new \UnexpectedValueException(
                sprintf('You cannot add data - you have to add a case first by using %s->addCase().', __CLASS__)
            );
        }

        $this->cases[$this->currentCaseTitle][$this->getParamTitle()] = $mixedData;

        return $this;
    }