Sorry, I don't Understand: Improving Voice User Interface Testing

Voice-based virtual assistants are becoming increasingly popular. Such systems provide frameworks to developers on which they can build their own apps. End-users can interact with such apps through a Voice User Interface (VUI), which allows to use natural language commands to perform actions. Testing such apps is far from trivial: The same command can be expressed in different ways. To support developers in testing VUIs, Deep Learning (DL)-based tools have been integrated in the development environments (e.g., the Alexa Developer Console, or ADC) to generate paraphrases for the commands (seed utterances) specified by the developers. Such tools, however, generate few paraphrases that do not always cover corner cases. In this paper, we introduce VUI-UPSET, a novel approach that aims at adapting chatbot-testing approaches to VUI-testing. Both systems, indeed, provide a similar natural-language-based interface to users. We conducted an empirical study to understand how VUI-UPSET compares to existing approaches in terms of (i) correctness of the generated paraphrases, and (ii) capability of revealing bugs. Multiple authors analyzed 5,872 generated paraphrases, with a total of 13,310 manual evaluations required for such a process. Our results show that, while the DL-based tool integrated in the ADC generates a higher percentage of meaningful paraphrases compared to VUI-UPSET, VUI-UPSET generates more bug-revealing paraphrases. This allows developers to test more thoroughly their apps at the cost of discarding a higher number of irrelevant paraphrases.