V-model in Software development model

 Generally There are different SDLC Models and methods that are developed and designed which are used during development process of a software system/application.Each process maintains particular life cycle in order to ensure that software is running developed successfully or not. The pattern of the life cycle goes in this way. It have 6 phases where each phase declares the deliverable s that are required by the next phase.

• Requirement Gathering: Requirements are gathered in this phase and a business requirement specification (B.R.S) document is prepared by business executives
• Analysis & Designing: System Analyst analyse the requirements and prepares the Design which will fit into the Client requirements
• Coding: Once designing is done according to HLD and LLD developers will develop the code for particular software or application
• Testing: After the code is developed the application/ software is tested by testers to check the proper working of the code.
• Deployment: After the testing is done the software/ application is delivered or deployed to the customer for their use.
• Maintenance: Once the application is launched and the users using it, then if any problem occurs that has to be handled by the developers for the long run of the product.

So after Waterfall model, V-model is sequential model which is more advantageous than Waterfall model. V- model means Verification and Validation model. Just like the waterfall model, the V-Shaped life cycle is a sequential path of execution of processes. Each phase must be completed before the next phase begins.  Testing of the product is planned in parallel with a corresponding phase of development.

Now we are going to know about verification and validation . Verification is nothing but it is a process we check whether the application we are building the system according to the requirements or not.Validation is nothing but it is a process where we check whether the application has been built according to the requirements or not,If we go through the diagram of the V-model clearly we can get an idea about the v-model.Simply it clearly says that the verification consists of reviews and inspections and validation consists of the unit testing and integration testing etc.,

• Requirements like BRS and SRS begin the life cycle model just like the waterfall model. But, in this model before development is started, a system test plan is created.  The test plan focuses on whether functionality is met or not for the specified requirements that are gathered.Here we do User acceptance testing.
• The high-level design (HLD) phase focuses on system architecture and design. It provide overview of solution, platform, system, product and service/process. An integration test plan is created in this phase as well in order to test the pieces of the software systems ability to work together.Here we go through the System Testing.
• The low-level design (LLD) phase is where the actual software components are designed. It defines the actual logic for each and every component of the system. Class diagram with all the methods and relation between classes comes under LLD. Component tests are created in this phase as well.
• The implementation phase is, again, where all coding takes place. Once coding is complete, the path of execution continues up the right side of the V where the test plans developed earlier are now put to use. that is nothing but integration testing.
• Coding: This is at the bottom of the V-Shape model. Module design is converted into code by developers. And they immediately do the unit testing.

Advantages of V-model:

• It is simple and easy to use.
• Testing activities like planning, test designing happens well before coding. This saves a lot of time. Hence higher chance of success over the waterfall model.
• Proactive defect tracking – that is defects are found at early stage
• Avoids the flow of defects.
• Works well for small projects where requirements are easily understood.

Disadvantages of V-model:

• Very rigid and least flexible.
• Software is developed during the implementation phase, so no early prototypes of the software are produced.
• If any changes happen in midway, then the test documents along with requirement documents has to be updated.

When to use this V-model:

The V-shaped model should be used for small to medium sized projects where requirements are clearly defined and fixed. The V-Shaped model should be chosen when ample technical resources are available with needed technical expertise. High confidence of customer is required for choosing the V-Shaped model approach. Since, no prototypes are produced, there is a very high risk involved in meeting customer expectations.