The penetration of electric vehicles (EV) is largely dependent on the number of settings and the charging rate of the corresponding electric vehicle supply equipment (EVSE). DC EVSE can transmit power to EV with high output power, that is called fast charging, which can greatly reduce charging time. EV and DC EVSE exchange information continuously through digital communication during charging to ensure the safety of charging in DC charging mode. Since manufacturers supplies variety of EVs and DC EVSEs in the market, implies that the components of the charging systems should extensively be tested to ensure interoperability between EVs and DC EVSE. This article introduces the digital communication conformance test for combined charging systems (CCS) based on DIN SPEC 70121 and ISO 15118 specifications.