## 1 Introduction  
V2X applications differ significantly from automotive applications. The automotive industry may focus on individual vehicle intelligence, enhancing Autonomous Driving (AD) capabilities through sensors, cameras, radars, and other equipment. In contrast, V2X applications emphasise the coordination among vehicles, pedestrians, roads, and the Cloud, where traffic participants share information through communication technologies to improve the safety and efficiency of the transportation system. Typical V2X applications include extended horizon driving, which expands the vehicle's range of perception by broadcasting information from surrounding vehicles and roadside devices. This surpasses the driving capabilities of individual vehicle intelligence, enabling functions such as the perception of events beyond the horizon and decision-making at traffic signal intersections. With the market-oriented development process of ICVs, vehicle makers have started to pay attention to the establishment of general testing and assessment systems for V2X-based applications. Testing is an essential guarantee for the security of V2X applications. The V2X test methods include function testing, performance testing, interoperability testing, conformance testing, gateway testing, penetration testing, and accelerated testing [1]. These tests can be performed in a laboratory environment with simulation tools, but the results obtained from the simulations fall short of fully supporting the safety considerations required for real-world applications. Consequently, field testing is a trend in V2X testing. Researchers and test institutions have developed several field test schemes in the past few years and implemented many tests in demonstrated areas, such as M-city [2] in Michigan, USA and AstaZero [3] in Sweden. These test schemes rely on controlled test sites. Moreover, most field tests adhere to traditional vehicle test rules, focusing on vehicle application testing, particularly for AD, while neglecting parallel assessments of communication performance [4]. V2X field testing, which aims to evaluate the corresponding application performance under complex traffic conditions, should provide both a communication performance testing function and an application response testing function [5]. The performance of Vehicle-to-Vehicle (V2V) safety applications is significantly influenced by the related factors of inter-vehicle communication, including vehicle node density, interference, noise, and environmental conditions. Notably, network congestion resulting from a high density of nodes stands out as a significant issue, as it not only diminishes the performance of the communication system but also leads to failures in V2V application responses [6]. Consequently, introducing large-scale testing involving numerous nodes is an efficacious approach to integrating application and communication testing. Based on the above analysis, we aim to implement a large-scale C-V2X automated field testing system (TS) that us tailored for combined scenarios. Several key concepts require clarification:  
* Communication and Application Scenarios Communication scenarios encompass communication channels and schemes that incorporate complex factors, including channel models, Doppler shifts, resource allocation strategies, and congestion control schemes. In a test case, two categories of vehicles are involved: key and environmental. Key vehicles pertain to the Host Vehicle (HV) and Remote Vehicle (RV), which are part of the application testing, whereas environmental vehicles are utilized to simulate scenarios with differing vehicle densities. Application scenarios depict specific instances or processes of an application, such as the 5 s immediately before and after a predicted collision in an FCW scenario. These scenarios encompass the microscopic motion characteristics (coordinates, speeds, accelerations, etc.) of the key vehicles and the surrounding environmental vehicles within the traffic environment.