UPDATE: The T now reports: "As of Sunday, June 16, Braintree branch riders will no longer need to switch trains at JFK/UMass."
As promised, the MBTA sent test trains down the repaired Red Line track at JFK/UMass today to see if it's ready for service on Monday. Only they ran into a problem that had nothing to do with the track: One of the test trains suffered mechanical problems and died - which led to 20-minute delays along the Braintree branch.