persist(a)               -> id assigned on the object: 1
find(Author, id)         -> Ann  (1 select)
getReference(Author, id) -> initialized: false  (0 selects)
merge(detached)          -> returns a different instance: true, name now Ann Smith
findMultiple(ids 3)      -> 3 entries, missing id gives: null
remove(a)                -> find afterwards: null