Waterfall Model Testing
Waterfall model testing describes testing performed as a single, distinct phase after development is entirely complete, following the traditional sequential waterfall methodology — requirements, design, development, testing, deployment — each phase finishing fully before the next begins.
Under waterfall, testing has no opportunity to influence requirements or design — by the time testers get involved, the system is already built according to a specification that was locked in much earlier, and any fundamental issues discovered during testing are comparatively expensive to fix this late in the process.
Its main advantage is thorough, comprehensive test planning against a complete, stable specification, which agile's evolving requirements can make harder — but it's fallen out of favor for most software specifically because defects and misunderstandings surface far later than in agile testing, when they're correspondingly more expensive to correct.
