WHY FOR SOFTWARE TESTING??

<font color=#550066> Test / Verification :</font> Testing /verification involves ensuring that functionality is correct. Such assurance can prevent time-consuming debugging at low abstraction levels and iterating back to high abstraction levels.
Simulation is the most common method of testing for correct functionality.
At the logic level, gate-level simulators provide output signal timing waveforms , given input signal waveforms.
General Purpose processor simulators execute machine code.
At the RT Level, Hardware description language ( HDL) simulators execute RT-Level descriptions and provide output waveforms, given input waveforms.
At the behavioral level, HDL simulators simulate sequential programs, and Cosimulators connect HDL and General Purpose Processor simulators to enable hardware/software co-verification.
At system level, a model simulator simulates the initial system specification using an abstract computation model , independent of any processor technology, to verify correctness and completeness of the specification.
Model checkers can also verify certain properties of the specification such as ensuring that certain conditions never occur ( in other words the system does not deadlock ).