An efficiency test, is a federally mandated requirement for Railroads, under 49 CFR part 217, to monitor rules compliance of the crews, for both Federal Law, and Railroad Operating and Safety Rules. What you experienced, was a required annual stop test, or what the FRA calls an Operational Monitoring Observation. Each engineer has to be checked at least annually, on stopping within 1/2 the range of vision under the requirements of Restricted Speed or it's operational equivalent, or compliance with fixed signal indications. These are unannounced checks, and there are dozens of types of tests, to check everything from stopping properly for signals or restricted speed, to proper wear of PPE, to handling of switches and derails, to protecting shove movements, and even compliance with drug and alcohol prohibitions.