A Combinatorial Approach to Multi-session Testing of Stateful Web Services

Most researches on web service testing have been focused on single session test where all messages are correlated. However, web services should support multisession interactions as part of the functional requirements. Concurrent multi-session testing is useful but non-deterministic. This paper proposes a combinatorial approach for multi-session test sequence generation by multiplexing single session test sequences.The paper shows that directly multiplexing operation sequences is impractical, and it introduces inverse operation sequence and condition combinations to reduce the search space. However, finding optimal operation sequences to completely cover the condition combinations turns out to be NP hard as it is equivalent to the classic set covering and Hamiltonian cycle problems. To address this issue, we introduce the concept of pivotal condition and devised a counting scheme to generate complete condition transition graphs for pivotal conditions. An efficient random walk algorithm is proposed to minimize condition transition graphs with guaranteed coverage of pivotal conditions. The proposed algorithms have been implemented and their performances are reported in the experimental results.