Combinatorial Testing of RESTful APIs

This paper presents RestCT, a systematic and fully automatic approach that adopts Combinatorial Testing (CT) to test RESTful APIs. RestCT is systematic in that it covers and tests not only the interactions of a certain number of operations in RESTful APIs, but also the interactions of particular input-parameters in every single operation. This is realised by a novel two-phase test case generation approach, which first generates a constrained sequence covering array to determine the execution orders of available operations, and then applies an adaptive strategy to generate and refine several constrained covering arrays to concretise input-parameters of each operation. RestCT is also automatic in that its application relies on only a given Swagger specification of RESTful APIs. The creation of CT test models (especially, the inferring of dependency relationships in both operations and input-parameters), and the generation and execution of test cases are performed without any human intervention. Experimental results on 11 real-world RESTful APIs demonstrate the effectiveness and efficiency of RestCT. In particular, RestCT can find eight new bugs, where only one of them can be triggered by the state-of-the-art testing tool of RESTful APIs.