In general, parallel testing involves testing multiple products or subcomponents simultaneously. A parallel test station typically shares a set of test equipment across multiple test sockets, but, in some cases, it may have a separate set of hardware for each unit under test (UUT).
The majority of nonparallel test systems test only one product or subcomponent at a time, leaving expensive test hardware idle more than 50 percent of the test time. Thus, with parallel testing, you can increase the throughput of manufacturing test systems without spending a lot of money to duplicate and fan out additional test systems.