The IceCube Upgrade will enhance IceCube’s capabilities at low and high energies. An important part of the Upgrade is the multi PMT approach: the new optical detector module, the multi-PMT digital optical module (mDOM), promises a large sensitive area, homogeneous solid angle coverage and the possibility of multiplicity triggering within a single module. In the past year the mDOM was tested and characterized to verify the design is up to requirements. During the mDOM Design Verification Test (DVT) phase, all the most basic features of the mDOM mainboard, the PMT bases and the calibration systems for the first DVT modules were tested. The next step will be the large-scale integrated mDOM Final Acceptance Testing to verify the previous measurements and the functionality of all subsystems while undergoing temperature cycles. In this poster the structure and the current state of the mDOM Testing will be presented. Some results of the Design Verification Tests will be shown as well as a short outlook for the upcoming Final Acceptance Testing (FAT).