Modeling and Testing Implementations of Protocols with Complex Messages
This addresses the challenge of ensuring correct message formatting and response handling in protocol implementations, particularly for domains like email servers, but it is incremental as it builds on existing formal methods for testing.
The paper tackles the problem of testing implementations of protocols with complex message structures by introducing APSL, a new language for formal description, and demonstrates its application in a case study on a Courier IMAP email server.
This paper presents a new language called APSL for formally describing protocols to facilitate automated testing. Many real world communication protocols exchange messages whose structures are not trivial, e.g. they may consist of multiple and nested fields, some could be optional, and some may have values that depend on other fields. To properly test implementations of such a protocol, it is not sufficient to only explore different orders of sending and receiving messages. We also need to investigate if the implementation indeed produces correctly formatted messages, and if it responds correctly when it receives different variations of every message type. APSL's main contribution is its sublanguage that is expressive enough to describe complex message formats, both text-based and binary. As an example, this paper also presents a case study where APSL is used to model and test a subset of Courier IMAP email server.