# A Survey of Vehicle to Everything (V2X) Testing
## 4 The Need for V2X Testing  
Since vehicles usually spend most of their time moving at high speed, it may have serious consequences when an accident happens and even threaten the safety of the driver and passengers [42]. Safety always has the highest priority, so how to ensure vehicle safety has always been a serious topic. In the field of traditional automobiles, various testing and evaluation systems have been established in all world countries. Testing is an indispensable part of the Internet of Vehicles which is a new thing for us. If a vehicle receives erroneous data in a specific environment such as a highway or a crowded area, it may cause false triggering of a safety application, resulting in a serious traffic accident. Testing can ensure the reliability of the communication, thus ensuring the safety of the entire V2X environment. Because of the high requirements for security of the V2X, the priority of V2X testing is also high. There are many problems in the Internet of Vehicles, which seriously hinder the development of vehicle networking technology and commercialization. Firstly, in special scenarios such as intersections or traffic jams, the density of vehicles is very large. The sheer number of users puts tremendous pressure on wireless communications, so it easily causes communication congestion [43]. Secondly, the vehicle has the characteristics of high mobility and rapidly changing network topology [44], which brings great difficulties to data transmission, routing, etc [45]. For example, two vehicles traveling in opposite directions will drive out of communication range within a few seconds. These communications have the requirement of low latency and high reliability for the Internet of Vehicles [46]. Finally, how to design and develop a good application is also an important issue for the Internet of Vehicles [47]. Before developing an application, developers need to spend a lot of time trying to determine the application scenarios. In addition, how to ensure the safety and effectiveness of an application is also an important issue [48]. Internet of Vehicles is a new cross-industry thing involving many industries such as automotive, communications, transportation, etc. As the name implies, V2X needs to connect all vehicles together, so the interconnection and interoperability are important attributes [49]. In the Internet of Vehicles, if a vehicle cannot understand the data sent by another vehicle with different brand, it will cause the lack of the information, and greatly reduce the meaning of V2X. Besides it may also lead to serious accidents resulting in unnecessary loss. At present, countries in which the V2X is growing up have been developing communication standards to help vehicles and other transportation participants to communicate unimpeded. These standards can also achieve understanding between different brands of vehicles and different intelligent transportation infrastructures, to ensure interconnection and interoperability of the V2X. Testing aims to ensure safe and effective use of the Internet of Vehicles. Different testing methods are adopted for different needs. Communication standards, as a common language among vehicles, infrastructures, clouds, etc., can help vehicles communicate with other traffic participants accessibly, enabling the interconnection and interoperability. Interoperability testing can ensure information exchange and coordination between devices [50]. The protocol conformance testing aims to verify the conformity of each manufacturer's terminals with standards [51]. They lay a foundation for the interconnection and interoperability between different manufacturers' devices. Different V2X applications have different communication performance requirements [52], such as automatic driving needing extremely low latency, and video entertainment applications requiring larger bandwidth.