Applicability of Coverage Criteria for Serverless Applications

Serverless computing is a popular trend in cloud computing based on serverless functions. These functions are stateless which can be utilized by the cloud platform provider to scale functions dynamically. While these small functions are easy to test in isolation, integrating them with other resources provided by the cloud platform provider or third parties creates a complex system whose emerging behavior is hard to test. Integration tests help test the interaction of the serverless functions with other resources and their environment. However, it is hard to decide if a test case is adequate and focuses on the critical parts of the system. Therefore, coverage criteria can be used to measure the coverage of the relevant software components and help assess the quality of the test suite. In this paper, we identified serverless applications based on serverless functions on GitHub and used them to investigate which coverage criteria can be used to capture the interaction of serverless functions with other resources. Furthermore, we show a general approach to implement the measurement of the coverage on FaaS platforms. Thus, developers have means to test the adequacy of their applications on any FaaS platform.