V-model

                                                     V-Model 

The V-model is an Software Development Life Cycle model where execution of processes happens in a sequential manner in a V-shape.
It is also accepted as Verification and Validation model.
The V-Model is an extension of the waterfall model and is based on the association of a testing phase for each and every  corresponding there development stage. This means that for every individual phase in the development cycle, there is a direct associated testing phase.

Advantages

• Nature : Flexible and rigid in nature 
• No Early prototypes : No early prototypes are produced because software is developed during the implementation phase. if any changes done then test document also updated on that time
• Systematic way : Process works in a systematic way
• Suitable : For large and small projects
• Testing : Testing is done at each and every phase even it's starts from requirement phase
• Track on progress : Easy to track it's process

Disadvantages

• Complex : Not suitable for complex and bigger projects.
• Rapidly Changes : If requirements of user are rapidly changing then it is not suitable for it
• Intervention : Client or user can"t see there project in between . they can see there project after completion . No intervention of user are allowed in between.
• Involve high risk and uncertainty

Where to use 
Where projects are small and there is less involvement of risk