Testing begins at the component level and works outward toward the integration of the entire computer-based system. Different testing techniques are appropriate at different points in time. The developer of the software conducts testing and may be assisted by independent test groups for large projects. The role of the independent tester is to remove the conflict of interest inherent when the builder is testing his or her own product

Verification - typically involves reviews and meeting to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meeting.

Validation - typically involves actual testing and takes place after verifications are completed. Validation and Verification process continue in a cycle till the software becomes defects free.

• PLAN (P) : Device a plan. Define your objective and determine the strategy and supporting methods required to achieve that objective.
• DO (D) : Execute the plan. Create the conditions and perform the necessary training to execute the plan.
• CHECK (C) : Check the results. Check to determine whether work is progressing according to the plan and whether the results are obtained.
• ACTION (A) : Take the necessary and appropriate action if checkup reveals that the work is not being performed according to plan or not as anticipated.