Netstub

Automated verification of distributed programs is a challenging problem. Since the behavior of a distributed program encompasses the behavior of the network, possible configurations of the network have to be investigated during verification. This leads to very large state spaces, and automated verification becomes infeasible. We present a framework that addresses this problem by decoupling the behavior of distributed programs from the behavior of the network. Our framework is based on a set of stub classes that replace native methods used in network communication and enables verification of distributed Java applications by isolating their behavior from the network. The framework supports two modes of verification: unit verification and integration verification. Integration verification checks multiple interacting distributed application components by running them in a single JVM and simulating the behavior of the network within the same JVM via stub classes. Unit verification targets a single component of a distributed application and requires that the user write an event generator class that utilizes the API exported by the framework. While unit verification only checks a single application component, it benefits from a greatly reduced state space compared do that of integration verification