V-Model in Software Engineering

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The V Model is a widely recognized and structured approach in software engineering that follows a systematic and well-defined process for developing high-quality software. It provides a comprehensive view of the software development lifecycle, incorporating requirements gathering, design, implementation, testing, and maintenance. The V Model in software engineering takes its name from the shape formed by the sequential and parallel phases of development and testing, which are aligned to ensure a comprehensive and rigorous approach. By following the V Model, software development teams can enhance efficiency, improve software quality, and mitigate risks throughout the development lifecycle.

What is a V-Model?

Every day we use multiple applications and software, and we notice how new features get added to our application every now and then. But we never think of how this application was developed first-hand, what all planning and processing might have happened. So in this article, we will study one of the popular software development life cycle models, known as the V Model, and will try to understand all of its features.

V model is a software development lifecycle model (SDLC) in which each step executes in a sequential manner with parallel testing for each development stage. The model is known as the V model because the diagram of the V model is quite similar to the V shape. V model is an extension of the Waterfall model, with the improvement that each development phase will go through a testing phase before moving forward. Thus this model is also known as the Verification and Validation model.

V model is a strict model as the development only moves forward when the previous step is completed, and this is made sure by doing testing after each development activity.

What is V Model

Let us understand this model with the help of the above diagram.

Here we can see that each development phase is associated with the testing phase. And the development and testing happen parallelly, which forms a V shape, as shown in the diagram. The left half of the V shape depicts Verification, and the right half depicts Validation, and both halves are joined by a coding phase which gives it a V shape.

In the verification phase, the static analysis happens; that is, it is checked whether the present phase meets its desired requirements or not without actually executing the code.

In the validation phase, the dynamic analysis happens; that is, it is checked whether the present phase meets the desired requirements that customers want from the software or not by executing the code.

V-Model Phases

1. Verification Phase of V-Model

The verification phase is the first phase of software development in the V Model. In the verification phase, the proposed model is verified across all the possible dimensions. In this phase, developers make sure that the model is fulfilling all business requirements. The verification happens in a sequential manner in various phases. The various phases are:

  • (i) Business Requirement Analysis

It is the very first phase of development. In this phase, the requirements and needs of customers are understood. What the customer expects from the final software, what functionalities customers want, and all such things are discussed in this phase. This is indeed a very important phase, as many times there is confusion in the mind of both customer and developer regarding the final outcome of the software. Acceptance testing is carried out in this phase.

  • (ii) System Design

In this phase, the actual design of the system is decided. After the requirement analysis phase, based on the finalized requirements, the complete design of the system is discussed. It includes the hardware and the communicating setup requirements.

  • (iii) Architectural Design

This phase is also referred to as High-Level Design(HLD). After the system design is analyzed, the architecture of the system is decided. It consists of various modules, database tables, UML diagrams, etc. In this stage, all the communications between the internal modules of the system and the outer system are understood.

  • (iv) Module Design

This phase is also known as Low-Level Design (LLD). After the high-level design is analyzed, each component in the high-level design is discussed in detail. The compatibility of each internal module and its feasibility is checked. Unit testing is performed in this phase.

2. Coding Phase of V-Model

This is the phase where actual coding and implementation take place. In this phase, the suitable programming language is decided based on the requirements. After code is written, it goes through multiple optimizations so as to produce the best possible functionality.

3. Validation Phase of V-Model

The different validation phases are:

  • (i) Unit Testing

Unit testing is performed in the module design phase. Here each module goes through the testing by executing the code written for that module. It tests whether each module is able to perform its required functions or not. If not, the bugs are removed so as to produce effective modules.

  • (ii) Integration Testing

Integration testing is performed in the architectural design phase. In integration testing, we check whether each module is working properly with other modules or not. In integration testing, we do end-to-end flow testing by integrating all the modules. The bugs related to the compatibility between modules are resolved in this phase.

  • (iii) System Testing

System testing is performed in the system design phase. Here the functionality of the whole system is checked by checking the integration of hardware and software and how well they are coordinating with each other. The interaction of the system, both internally and externally, by means of hardware and software is tested. All the bugs related to hardware or software issues are resolved here.

  • (iv) Acceptance Testing

User Acceptance testing happens in the requirement analysis phase. Here the system is checked in the user environment. If there is any problem in the user environment or there is any issue regarding compatibility with the other software available in the user environment then that is removed in this stage.

4. Industrial Challenge

As the software industry has progressed, technologies have grown in complexity with constant evolution. Despite these advancements, certain fundamental principles and concepts continue to hold true, just as they did in the early days of IT. These principles include:

  • Precisely defining and continuously refining user requirements.
  • Designing and constructing applications in alignment with the approved user requirements.
  • Ensuring that the developed application follows business requirements through validation processes.

Principles of V-Model

  1. Scalability: This principle enables the V model to scale the project into bigger and more complex projects. It makes the V model flexible toward changing the magnitude of cost and complexity.

  2. Large to Small: In the V model, we start with requirement analysis which takes into account all the aspects of the project like system, cost, and feasibility. Then we move to system design which talks about the whole system, hardware, and software, and then we move towards high-level design, which discusses all the modules and their interactions with each other, and then to a low level which talks about each module internally.
    Thus we start from the largest part(requirement analysis), and then we slowly move toward the smallest part(low-level design).

  3. Data and Process Integrity: According to this principle, there should be the integrity of data and process in the project. That is, there should be no redundancy or ambiguity in the data or process at any phase of development. And there should be cohesion between data and process at each stage of development.

  4. Tangible Documents: This principle of the V model focuses on the importance of documentation. Documentation of the project must be made and maintained at each phase of development and testing. This documentation is further used by developers and users interacting with the project in the future.

  5. Cross Referencing: This principle states that each development phase is directly referenced by the corresponding testing phase and each testing phase is directly referenced to the corresponding development phase. Thus making the cross-referencing.

Applications of V-Model

  • The V Model provides a structured and systematic approach to software development, enhancing organization and efficiency.
  • It emphasizes the alignment of development and testing activities, enabling early defect identification and resolution.
  • The V Model ensures thorough verification and validation of the software throughout the development lifecycle.
  • The V Model promotes documentation and traceability, facilitating transparency and future enhancements.
  • It is often used in industries with stringent regulatory requirements, aiding in compliance and adherence to guidelines.
  • The V Model encourages collaboration between development and testing teams, improving communication and teamwork.
  • It provides a framework for project management and control, enabling progress tracking and effective resource management.

When to Use V-Model in Software Engineering?

V model is quite similar to the waterfall model, with the only difference being that there is parallel testing in the V model but not in the waterfall model. Thus the V model can be used wherever the waterfall model is used.

Some important points to look upon before deciding to use the V model are:

  1. Project requirements should be very clear and fixed.
  2. There should be clarity about the technologies being used in the project.
  3. All the members of the team working on a project should be well aware of the requirements and technologies of the project.
  4. The project should be short as it is difficult in large projects to maintain fixed requirements.

Advantages and Disadvantages of V-Model

Advantages of V-ModelDisadvantages of V-Model
Very simple and easy-to-use SDLC V modelNot Suitable for complex projects
Very easy to manage as the development happens in a sequential manner, and the next phase starts only when the previous phase is completeNot suitable for projects having unclear or changing requirements
Ideal model for short and rigid projectsNot suitable for projects wanting concurrency in the development phase
Verification and validation at each step of development ensures that the final product will be bug-freeVery risky and uncertain SDLC V model
Project management is quite easy as compared to other software development models--


  1. Very simple and easy-to-use SDLC V model.
  2. Very easy to manage as the development happens in a sequential manner, and the next phase starts only when the previous phase is complete.
  3. Ideal model for short and rigid projects.
  4. Verification and validation at each step of development ensure that the final product will be bug-free.
  5. Project management is quite easy as compared to other software development models.


  1. Not suitable for complex projects.
  2. Not suitable for projects having unclear or changing requirements.
  3. Not suitable for projects wanting concurrency in the development phase.
  4. Very risky and uncertain SDLC V model.


In a nutshell, the V model allows parallel validation and verification at each step. It is very good for projects having pre-defined and fixed requirements. But it is not suitable for large and complex projects having uncertain requirements. Since there is verification at each step, we are sure that each step is executed correctly, and we do need to check all the previous steps when we encounter any bugs. Thus, if you have a simple project and all customer requirements are clear, then the V model is a suitable choice for your project.