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Difference between V-model and W-model | Software Testing QA / Software Testing

Jul 08, 2020 Namiko

Difference between V-model and W-model | Software Testing

How are V and W models different by definition?

The software development process is a strategy in which a product is made to go through different phases, such as ideation, arranging, creation, and testing, before the end product is conveyed.

The big difference is, as a prerequisite for the Waterfall model, testing can only happen once the development of the software product is finished without any adjustments in the middle. The W model is a straightforward successive approach in which the progress flows in just one direction.

On the other hand, V Model, also called Verification and Validation Model, is like the waterfall model that takes a successive way of executing procedures. In that sense, we can say V-model is the alternative to the W-model as steps are followed as requirements, design, implementation, verification, and maintenance.

The V-model has been a staple in software quality testing since its introduction to the market back in the 1980s. Its sequence of steps is designed so that each phase builds upon the completion of preceding tasks, forming an upwards-bent progression for maximum efficiency and execution accuracy.


1) Verification phase includes

  • Business requirement review is where clear communication, including exact functions and requirements, and acceptance test design planning is held.
  • The system design stage involves understanding and detailing the product’s hardware and communication setup. System test design is best to be planned at this stage.
  • The architectural design stage is where high-level design is developed. Along with understanding the technical and financial feasibility of the product before it is developed. An integration test is best to be planned at this stage.
  • The module design stage focuses on designing a detailed plan for the internal modules of the system, also known as low-level design; it is vital to ensure that the invention is compatible with other surrounding modules in system architecture.

2) Coding phase includes

Here, the actual coding of the system modules is taken up. Based on the system and architectural requirements of the program, the best suitable programming language is selected. Then the code is reviewed and optimized to ensure the delivery of best performing as well as unit testing completed by the developers.

3) Validation phase includes

  • Unit testing is conducted early so that the bugs are eliminated at the early stages of product development, though not all bugs can be revealed.
  • Integration testing is done to check whether there is valid and proper communication within the internal modules of the system.
  • System testing is the testing of the entire system to ensure that the internal modules are configured to communicate effectively with the external systems.
  • Acceptance testing is done to test a product in the client’s environment to check compatibility issues.

Advantages of the V model:

  • Simple and explicit process to follow
  • Testing starts from the requirement phase itself
  • All the Functional Areas can be covered
  • Defects can be found at an early stage

This is comparable to the shift-right approach in DevOps testing, which encourages the testers to analyze and wait until changes are deployed in production to find defects in unexpected real-life situations.

With the same definition of each phase – Requirement Review, System Design, Architecture, Low-level Design, using W model helps ensure that the testing of the product begins from the very first day of the product’s development.


Advantages of the W model:

  • Testing can run in parallel with the development process
  • No division between constructive and destructive tasks
  • Often Developer is responsible for removing defects

Disadvantages of the W model

  • Complex to track the progress
  • Testing has equal weight and workload as many activities in the development process

It embodies the shift-left testing approach ‘test early and often’ to perform testing earlier in the lifecycle thereby moving left on the project timeline.


While it is true that the V model is an effective way to test and reveal results for dynamic test cycles, there is no scope for risk management and mitigation for scheduling especially. In contrast, W models are more effective in catching defects early in the delivery pipeline and enable the development team to get an extensive view of testing. However, important to remember that the W model is often compared to agile testing where testing happens in parallel which requires a significant amount of resources throughout the product cycle.

One must pick carefully, a model that works better with the available pool of resources and the complexity of each project in order to convey an ideal quality product.


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