## 8 Conclusions  
In the realm of ICV, its profound integration across industries stands out as a notable characteristic, and it also presages the development of general testing and assessment systems as an inevitable trend. Currently, most test schemes are centered on application testing, ignoring the comprehensive integration requirements of various test types, such as communication, interoperability, consistency, and network security. Notably, OEMs have paid keen attention to how the communication environment impacts the response characteristics of applications.  
Given our previous work constructing a large-scale C-V2X testing system for communication testing, we recognize that integrating communication testing with application testing poses significant challenges to system software development. Consequently, we propose a layered software architecture for a highly automated, large-scale C-V2X testing system tailored to combined scenarios.  
At the core of this architecture lies the scenario encapsulation technology, which enables communication testing and application validation under many scenarios through the deployment of a flexibly adjustable node array. Furthermore, during the architectural design process, we thoroughly considered the system's non-functional requirements, encompassing real-time system status monitoring, high-concurrency data-processing capabilities, real-time data management, and a user-friendly online visualization interface.  
The experimental results demonstrate that the proposed layered architecture, along with the communication protocol and technology stack that were used, fulfills the requirements for the TS in terms of validity, scalability, and stability.  
For future work, we will continuously optimize the TS and further explore digital twin TS grounded in the integrated vehicle-road-Cloud framework. By leveraging efficient information interaction and coordination mechanisms among vehicles, road infrastructure, and cloud servers, we will construct digital test scenarios and investigate V2X test strategies in which the testing and actual operation reinforce each other, thereby enhancing test coverage and efficiency.  
Conceptualization, Q.H., L.Z., L.Y. and F.X.; methodology, L.Z., M.Z. and F.X.; software, M.Z., M.T. and F.X.; validation, L.Z., Q.H. and L.Y.; formal analysis, L.Z., M.Z., M.T. and F.X.; investigation, L.Z., M.Z., M.T. and F.X.; resources, L.Z., Q.H. and L.Y.; data curation, L.Z. and F.X.; writing--original draft preparation, Q.H. and M.Z.; writing--review and editing, Q.H., M.Z., L.Z., L.Y., M.T. and F.X.; visualization, M.Z. and M.T.; supervision, L.Z. and Q.H.; project administration, L.Z.; funding acquisition, L.Z., Q.H. and L.Y. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Chongqing Technology Innovation and Application Development Special Project (Grant No. CSTB2022 TIAD-STX0001 and Grant No. cstc2021 jscx-gksbX0057) from the Chongqing Science and Technology Bureau.  
Not applicable.  
The data presented in this study are available on request from the corresponding author. The data are not publicly available due to privacy.  
The authors declare no conflicts of interest.