REST API Functional Tester

Software developers nowadays routinely publish REST APIs to make their applications accessible to clients. To support the development of REST APIs, many testing techniques and tools have been developed that automatically explore the API endpoints, using various strategies, intending to increase coverage and detect bugs. However, these techniques can produce test cases that may not be suitable for creating functional test suites. In this paper, we address the problem of automatically generating realistic functional test cases for REST APIs. Our work is guided by interactions with practitioners and the approaches they follow for performing functional testing of REST APIs. Our technique first groups the API operations by the resources they manipulate; it then employs a novel approach for inferring producer-consumer relations between operations, fine-grained subtyping of HTTP methods, and language-model-based sequencing to construct operation sequences that correspond to functional scenarios. We evaluated the effectiveness of our technique and compared it against state-of-the-art REST API testing tools. Our results show that the technique produces test cases that can better support functional testing of REST APIs than the other tools.