  The widespread adoption of DNNs in NLP software has highlighted the need for
robustness. Researchers proposed various automatic testing techniques for
adversarial test cases. However, existing methods suffer from two limitations:
weak error-discovering capabilities, with success rates ranging from 0% to
24.6% for BERT-based NLP software, and time inefficiency, taking 177.8s to
205.28s per test case, making them challenging for time-constrained scenarios.
To address these issues, this paper proposes LEAP, an automated test method
that uses LEvy flight-based Adaptive Particle swarm optimization integrated
with textual features to generate adversarial test cases. Specifically, we
adopt Levy flight for population initialization to increase the diversity of
generated test cases. We also design an inertial weight adaptive update
operator to improve the efficiency of LEAP's global optimization of
high-dimensional text examples and a mutation operator based on the greedy
strategy to reduce the search time. We conducted a series of experiments to
validate LEAP's ability to test NLP software and found that the average success
rate of LEAP in generating adversarial test cases is 79.1%, which is 6.1%
higher than the next best approach (PSOattack). While ensuring high success
rates, LEAP significantly reduces time overhead by up to 147.6s compared to
other heuristic-based methods. Additionally, the experimental results
demonstrate that LEAP can generate more transferable test cases and
significantly enhance the robustness of DNN-based systems.
