Currently for the European Space Agency (ESA) ATHENA [1,2] mission Silicon Pore Optic (SPO) [3-8] Mirror Modules (MM) with a focal length of f = 12 m, are being developed and tested. The SPO MMs are also the baseline optic for the NASA medium explorer high-resolution spectroscopy mission Arcus [9-10] with f = 12 m that is currently undergoing a phase A study. SPOs are currently being tested at both the PTB laboratory of the BESSY synchrotron facility in Berlin using an X-ray pencil beam and the PANTER X-ray test facility in Neuried of the Max-Planck-Institut für extraterrestrische Physik, Garching using a long vacuum beamline (distance source to optic ~120 m). The different types of measurements performed at PANTER to characterise the ATHENA and Arcus optics will be discussed. This will be done on the level of an X-ray optical unit (XOU) composed of both a primary and secondary High Performance Optic (HPO) stack, a mirror module (MM) composed of two XOUs, small (<4 MMs) and large (< 25 MM) petals, and the complete integrated optic Athena (700-1000 MMs) and Arcus (4 petals each with 38 MMs). The main set of tests that are currently done at PANTER make full use the possibility to fully-illuminate single XOUs, MMs, and petals to determine their optical characteristics such as the half energy width of the point spread function as well as the effective area and the vignetting function at different energies. To ensure that the measurements, that are required to demonstrate the performance of ATHENA, are possible, a description of recent and upcoming upgrades to the PANTER X-ray test facility will be given. Finally, a status update on the progress on designing the new facility to be used to test and calibrate the complete ATHENA mirror will be presented.