Test case generation of onboard ATP for heavy haul rail based on hybrid whale optimization algorithm

Combinatorial Testing (CT) of the onboard Automatic Train Protection (ATP) function in heavy haul railway train control systems can significantly enhance equipment safety. However, the large number of input parameters influencing ATP correctness, combined with complex inter-parameter constraints, often results in redundant test cases and combinatorial explosion. To address multi-parameter interactions, this study proposes a Hybrid Whale Optimization Algorithm (HWOA)-based test case generation method, using the train overspeed protection scenario as a case study. First, the key parameters affecting ATP overspeed protection are identified based on the train control system’s requirements specification. Next, parameter interactions are analyzed to construct a combinatorial testing model that satisfies the constraints. To meet the testing requirements of the onboard ATP system, the Q-learning algorithm dynamically optimizes the control parameters of the Whale Optimization Algorithm (WOA), enabling adaptive search strategy adjustments and balancing exploration-exploitation phases. Additionally, a Lévy flight disturbance strategy is introduced to expand the optimal solution search space, preventing local optima entrapment and premature convergence, thereby generating a constraint-compliant test suite. The proposed algorithm is validated using the Shuozhou-Huanghua Railway train control system simulation platform, incorporating real-world track data and equipment parameters. Results demonstrate that, compared to the standard WOA, the HWOA reduces test case counts by 13.3%, 11.4%, and 6.7% at coverage strengths of 2, 3, and 4, respectively, while shortening generation time by 0.156 s, 1.23 s, and 3.09 s. Furthermore, the HWOA exhibits faster convergence, higher accuracy, and superior search capability when benchmarked against WOA, PSO, and APSO algorithms. These findings provide valuable insights for the safety validation of heavy haul railway onboard ATP systems.