# A Survey of Vehicle to Everything (V2X) Testing  
[PERSON]  
1 College of Computer Science and Technology, Jilin University, Changchun 130012, China; [EMAIL_ADDRESS]  
[PERSON]  
1 College of Computer Science and Technology, Jilin University, Changchun 130012, China; [EMAIL_ADDRESS]  
[PERSON]  
3 Technology and Standards Research Institute, China Academy of Information and Communications Technology, Beijing 100191, China; [EMAIL_ADDRESS] (Y.G.); [EMAIL_ADDRESS] (R.Y.)  
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of V2X communication and its performance requirements. LTE-V2X is a wireless communication technology for V2X with high data rate and controlled QoS [11; 12], which is based on the evolution of LTE mobile communication technology defined by 3 GPP, including two kinds of working modes of cellular communication (Uu) and direct communication (PC5) [13; 14; 15; 16]. The Uu mode uses the existing LTE cellular network to implement V2V communication by forwarding (shown in Figure 1a), and the PC5 mode is similar to the DSRC, enabling direct communication between vehicles (shown in Figure 1b) [17; 18]. Additionally, the PC5 interface has been enhanced in many aspects to accommodate exchanges of rapidly changing dynamic information (position, speed, driving direction, etc.) and future advanced V2X services (automatic driving, vehicle platooning, sensor sharing, etc.) [19].  
The application of V2X involves many aspects, such as intelligent transportation, intelligent connected vehicles, and automated driving [20]. Different applications have different requirements for latency, reliability, throughput, user density, and safety of the V2X environment [21]. Safety applications and automated driving require extremely low latency and a secure network environment [22; 23]. For example, vehicles usually spend most of their time moving at high speed and malicious attackers could cause serious traffic accidents by broadcasting false messages. Malicious attackers may also obtain a vehicle owner's identity information, vehicle location information, driving trajectory, and so on by interception of data packets [24]. This violates user privacy. The V2X data includes information about roads and geography, which relates to national security. Therefore, security is the top priority for V2X [25].  
Testing is an important mean to ensure the safety and security of a vehicle. The V2X test is conducted to identify specification flaws, design flaws, and implementation defects over the entire life cycle, and to determine the root cause of the problem [26]. Modeling, analyzing, testing, and evaluating the security threats to V2X can help to improve the security protection capabilities of vehicles and promote the construction of vehicle security systems. In addition, by carrying out testing for V2X, we can pave the way for the commercialization of automatic driving and other applications.  
The structure of this paper is as follows: Section 2 summarizes the types of V2X applications. Section 3 analyzes latency/reliability challenges and security challenges and summarizes the possible security threats. Section 4 describes why we need to do V2X tests and which types of tests should we do. Section 5 lists and briefly analyzes the test objectives and test methods of V2X. Section 6 proposes an end-to-end testing system combining virtual and real environments which can undertake the test task of the full protocol stack.