The paper describes methodology and corresponding environment for development, validation and testing of complex electric vehicle (EV) systems. The proposed approach is based on distribution of relevant design tasks between remotely working testing equipment with real-time (RT) data sharing and data exchange. The approach is demonstrated by the example of X-in-the-loop (XIL) environment uniting electric motor test setup, hardware-in-the-loop (HIL) platform with brake-by-wire system, and the brake dynamometer. The study introduces how this configuration of experimental tools can be used by designing the brake blending and control of an EV.