Testing is the process of identifying bugs and ensuring software meets requirements. It involves executing programs under different conditions to check specification, functionality, and performance. The objectives of testing are to uncover errors, demonstrate requirements are met, and validate quality with minimal cost. Testing follows a life cycle including planning, design, execution, and reporting. Different methodologies like black box and white box testing are used at various levels from unit to system. The overall goal is to perform effective testing to deliver high quality software.