A system for testing a global navigation satellite system (GNSS) receiver includes signal generators, antennas coupled to respective signal generators and having overlapping antenna radiation patterns, and processing circuitry. The signal generators generate respective test signals. Each of the test signals is a combination of multiple GNSS navigational signals which are generated using a set of ranging codes. The processing circuitry selects respective sets of ranging codes for the signal generators, such that the sets of ranging codes are separately insufficient to lock a GNSS receiver and are jointly sufficient to lock a GNSS receiver.