V Model (Verification and Validation model)

V - Model means verification and validation model . Each phase should be completed before starting the next phase, In this model testing will be done parallel with the corresponding phase of development

Why V model is in "V" shape ?

Validation phase completely depends on the verification phase (Acceptance testing completely depends on BRS, System testing  depends on SRS, Integration testing depends on HLDS, Unit testing depends on LLDS) so we can draw only this diagram in V shape

Verification phase should be carried out from SDLC(software development life cycle) and validation phase should be carried out  from STLC.

V Model starts from the Requirement gathering , Business analyst(BA) gathers all the requirements from the client and prepare BRS(Business Requirements Specification) document. BA will review that document after completion of the requirements gathering, System Analyst will prepare the SRS(System Requirements Specification) based on the BRS, and SA will review that document after completing that document.

Technical architect (TA) will prepare HLDS(High level designs) based on SRS and  TA will review that document after completing that document, Developers will prepare LLDS(Low Level Designs)

and developers will review that LLDS, After that developers will start coding and they will do unit testing with the help of LLDS, after that they will do integration testing with the help of HLDS, after that Testing team will test the application with the help of SRS.
Acceptance testing will be done based on BRS.

Advantages:

--> For  small projects V model is very useful

--> Review activities are performed in each and every stage(ex: BRS, SRS, HLDS, LLDS...etc)

---> Most of the bugs are found early in life cycle.