Yes, they are tested in a lab on a dyno that simulates air resistance by increasing the resistance on the dyno roller.
EPA actually asks for several other tests, some of which would probably be very usefully if shared with the consumer. But I assume manufacturers only want to share the portion of the test they are legally required to.
SFTP-SC03: Test with AC on and lab temp at 95F.
SFTP US06: An aggressive highway test at 80 MPH, sometimes called "superhighway" test.
FTP 72: Test for stop and go traffic, sometimes called "supercity" test.
Link below shows the driving schedule and conditions of each test.
