Test process
  Testing operates in parallel to the development process
  Unit tests are written and applied by the developer
  They are applied when the developer is ready
  Subsystem tests are often written and applied by an
“integration” team
  These integrations or “builds” are scheduled when all the
classes in a subsystem are ready
  System tests are written and applied by a system test team.
  Scheduled when sufficient end-user functionality is available
to test