The provider of this task will be responsible for planning and executing User Acceptance Testing (UAT), and for planning and facilitating interoperability testing between the MARI platform and external systems of the participating TSOs (IOP). Part of the preliminary phase will be to participate in Factory Acceptance Tests (FAT) which will be executed and facilitated by providers of software development Unicorn and Artelys. In cooperation with the project, the UAT phase needs to be planned: test cases, test scenarios, expected performance and benchmarking against mFRR platform requirements catalogue in its most current version. During the UAT, the provider must be in a position to carry out these tests, mostly independently (possibly with the involvement of Unicorn), and report to the project on the results, issues encountered and possible counter-measures on a regular basis determined by the project. A final test report is expected, so that the project can assess the results of the developed version and decide on next steps (exit criteria).