public function execute(array $args, FunctionProphecy $function)
    {
        if (is_string($this->exception)) {
            $classname = $this->exception;
            $reflection = new ReflectionClass($classname);
            $constructor = $reflection->getConstructor();

            if ($constructor->isPublic() && 0 == $constructor->getNumberOfRequiredParameters()) {
                throw $reflection->newInstance();
            }

            if (!$this->instantiator) {
                $this->instantiator = new Instantiator();
            }

            throw $this->instantiator->instantiate($classname);
        }

        throw $this->exception;
    }