What can I expect at a hearing test for my baby?

Passing it. Babies should be passing their hearing tests. If failing it at birth then needs repeat test and might need further testing. If fails hearing later on in life, then might be attributed to wax, fluid in ears, infection, or some other abnormality to the inner ear.
See if baby has hear. Most of the hearing tests on the babies are fine and if the baby fails it needs to be repeated newborns can not be called deaf until they fail two or more tests.
Depends on age. Hearing screening done in the newborn period (called algo) is done by putting headphones on the baby and testing while the baby is calm or sleeping. This testing is quite easy. After 12 months of age, a baby who needs hearing tested can have behavioral audiology. In between, baby is too young to respond adequately so hearing testing must be done via brain stem responses, requiring sedation.