What is V - Model - Advantages, Disadvantages And When to use it

V - Model :- V - Model testing means "Verification and Validation Model". Like the Waterfall model, the V shaped life cycle is a sequential path of execution of processes. Each phase should be completed before the next phase begins. Testing of the product is done parallel with a corresponding phase of SDLC. That is also called Review, Inspection or Static Testing.
When to use V - Model :-
Where time and cost is the constraints of the project then, we can use such models for quick and cost effective delivery. In comparison with Waterfall model, V model is more or less the same, but the activity of testing starts very early. Whcih leads to less time and cost of the project.

Let's discuss Verification and Validation Phase in detail :- 

Verification Phase :-

1. BRS (Business Requirement Specification) :- This phase includes studying the product requirements from the customer perspective.
2. SRS (System Requirement Specification) :- Deals with understanding and detailing the hardware and communication setup for the product under development.
3. HLD (High Level Design) :- SRS can be broken down further into modules taking up different functionality which is also referred to as High Level Design. It is also called Architectural Design.
4. LLD (Low Level Design) :- The internal design for all the system modules is listed out and is also known as LLD. It is also called Module Design.
5. Coding :- In this phase developer writes code.

                        Validation Phase :-

1. Unit Testing :- Unit test cases that were created in the Low Level Design phase are executed in Unit Testing. Unit Testing is conducted by developers only. In this testing, developer test code to find out any bugs or problem in the particular unit or module.

2. Integration Testing :- In Integration Testing the integration test cases which were created in the Architectural or High Level Design phase are executed. In this phase, we integrate more then one unit or module together to find out any cause or bug during  the interconnection of different different units or modules together. This phase is conducted by developer and tester both.

3. System Testing :- In System Testing functional and non-functional test cases are executed. This testing is associated with System Requirement Specification (SRS) phase. In this tester checks the entire system for its correctness and completeness.

4. Acceptance Testing :- Acceptance Testing is conducted to make sure that the Business Requirement Specification (BRS) are met in the user environment. In this testing we also uncover the compatibility and non-functional issues like performance, load, stress etc.

Advantages of V-Model :- 

* It is very good approach to choose V-Model, where projects are small and easy to understand. As it is very easy to use.

* In V-Model one phase is completed before the next phase is begin.

* Works well where Requirements are clearly defined.

* Easy to manage due to robustness of the model.

Disadvantages of V-Model :-

* High risk and less flexibility.

* Not a good model for large and complex projects.

* Not good where requirements are frequently change.

* Working software is not available until the last phase of the life cycle.