Modbat: A Model-Based API Tester for Event-Driven Systems

Model-based testing derives test executions from an abstract model that describes the system behavior. However, existing approaches are not tailored to event-driven or input/output-driven systems. In particular, there is a need to support non-blocking I/O operations, or operations throwing exceptions when communication is disrupted. Our new tool “Modbat” is specialized for testing systems where these issues are common. Modbat uses extended finite-state machines to model system behavior. Unlike most existing tools, Modbat offers a domainspecific language that supports state machines and exceptions as firstclass constructs. Our model notation also handles non-determinism in the system under test, and supports alternative continuations of test cases depending on the outcome of non-deterministic operations. These features allow us to model a number of interesting libraries succinctly. Our experiments show the flexibility of Modbat and how language support for model features benefits their correct use.