Property-Based Testing of JSON Based Web Services

This article describes a systematic approach to testing behavioural aspects of Web Services that communicate using the JSON data format. As a key component, the Quviq QuickCheck property-based testing tool is used to automatically generate a large number of test cases from an abstract description of the service behaviour in the form of a finite state machine. The same behavioural description is also used to decide whether the execution of a test case is successful or not. To generate random JSON data for populating tests we have developed a new library, jsongen, which given a characterisation of the JSON data as a JSON schema, automatically derives a QuickCheck generator which is capable of generating an infinite number of JSON values that validate against the schema.