Neither advocates skipping integration and system testing. The boundary that defines the scope of unit and integration testing is different for object-oriented development. Tests can be designed and exercised at many points in the process. The scope of testing corresponds to the collaborations necessary to accomplish the responsibility under test. As the scope of integration in an application system approaches all components in the system, the appropriate testing techniques are very similar to conventional system testing.
Testing is trivial.
Testing is simply poking around until you run out of time. All we need to do is start the app, try each use-case, and try some garbage input. Hunches about testing completeness are notoriously optimistic. Adequate testing requires a sophisticated understanding of the system under test. You need to be able to develop an abstract view of the dynamics of control flow, data flow, and state space in a formal model.