This summer marked the continuation of a successful series of RS-25 engine tests at NASA's Stennis Space Center. From NASA:
"NASA engineers closed a summer of successful hot fire testing Aug. 30 for flight controllers on RS-25 engines that will help power the new Space Launch System (SLS) rocket, being built to carry astronauts to deep-space destinations, including Mars. The space agency capped off summer testing with a 500-second hot fire of a fifth RS-25 engine flight controller unit on the A-1 Test Stand at Stennis Space Center near Bay St. Louis, Mississippi. The controller serves as the “brain” of the engine, communicating with SLS flight computers to ensure engines are performing at needed levels. The test marked another step toward the nation’s return to human deep-space exploration missions."