The testing activity assesses the considered monolithic sensor technologies in view of the performance and radiation-hardness requirements by means of measurements on test chips and related data analysis. The activity develops standardised infrastructure, tools and procedures for efficient measurements on a variety of generic test structures and test matrices. The foreseen measurements include functional tests and operation-parameter optimisations, measurements of the response to electrical pulses, photon and light sources, radiation resistance tests (ionising and non-ionising) as well as measurements with particle beams using beam-telescope setups. The testing effort is broadly distributed across the collaboration and the EP R&D work package, allowing external partners to have access to samples and contribute to the overall characterisation challenge.