A simulation environment with the focus on testing multi-antenna GNSS receivers under challenging signal conditions including GNSS jamming and spoofing. The central element of the facility is a multi-output GNSS Constellation Simulator composed of eight simulation units of the GSS9000 series of Spirent. The simulator can therefore support scenarios including up to eight independent antennas and users, with an individual RF signal generated for every simulated antenna. In case of testing a GNSS receiver with a controlled reception pattern antenna (CRPA), the antennas are arranged in an array configuration that is carried by a user platform. The GSS9000 units are precisely phase-aligned, which enables to simulate the directions of arrival of all generated signals. Additionally, each GSS9000 unit is equipped with two high-power signal cards used to generate strong jamming signals with up to 100 dB of interference-to signal ratio. The facility also includes other pieces of measurement equipment which can be used to support the simulations: auxiliary RF signal generator, spectrum analyser, multi-channel record and playback device, reference GNSS receivers etc. All these features make the MASTER simulation environment a powerful tool for testing multi-antenna and CRPA receivers under controlled and reproducible signal conditions.