  The limits imposed by the classical cosmological tests on closed and open FRW
universes driven by adiabatic matter creation are investigated. Exact
expressions for the lookback time, age of the universe, luminosity distance,
angular diameter, and galaxy number counts versus redshift are derived and
their meaning discussed in detail. An interesting consequence of these
cosmological models is the possibility of an accelerated expansion today (as
indicated from supernovae observations) with no need to invoke either a
cosmological constant or an exotic "quintessence" component.
