Abstract: A mobile container system includes a first and a second standard-sized container releasibly securable together, and arranged in parallel in a longer direction. Each container has a cuboid metal frame with standard-sized corners, and are attached to each other with reinforcement beams The containers are secured via locking means arranged between at least one standard-sized corner or reinforcement beam of the first container and corresponding standard-sized corner or reinforcement beam of the second container. A portion of side walls of the respective containers, facing each other, are removed to provide enlarged interior space extending at least partially over both containers. As a mobile test unit system, a portion of the side walls are removed to provide enlarged interior operating space as a test room extending over both containers A vehicle component is included exchangably arranged within the test room. Also provided is a fire protected enlarged interior.