Passive Testing of Web Services

This paper presents a methodology to perform passive testing based on invariants of distributed systems with time information. This approach is supported by the following idea: A set of invariants represents the most relevant expected properties of the implementation under test. Intuitively, an invariant expresses the fact that each time the system under test performs a given sequence of actions, then it must exhibit a behavior reflected in the invariant. We call these invariants local because they only check the correctness of the logs that have been recorded in each isolated system. We discuss the type of errors that are undetectable by using only local invariants. In order to cope with these limitations, this paper introduces a new family of invariants, called globals to deal with more subtle characteristics. They express properties of a set of systems, by making relations between the set of recorded local logs. In addition, we show that global invariants are able to detect the class of undetected errors for local invariants.