The Free On-line Dictionary of Computing (18 March 2015):
(Or "application testing") A type of testing to
confirm that all code modules work as specified, and that the
system as a whole performs adequately on the platform on
which it will be deployed.
System testing should be performed by testers who are trained
to plan, execute, and report on application and system code.
They should be aware of scenarios that might not occur to the
end user, like testing for null, negative, and format
inconsistent values. A tester should be able to repeat the
steps that caused an error.