From the beginning, information technologies recognized the importance and importance of developing and applying a set of standards, methodologies, life cycles and best practices that all practitioners can apply. As the industry evolved, the technologies became more complex, more rapid and constantly changing, but there remains a set of basic principles and concepts that are just as applicable today as at the early stage of the IT industry development.

One of the initial concepts created and applied by the first IT specialists was the V-model.

The V-model developed in the 1960s, since that time it has been repeatedly processed, improved and extrapolated. There are many versions of the V-model, each with its own specialized terminology, names and descriptions of phases. Although the IT industry has undergone major changes since its inception, the principles defined by the V-model are as applicable today as they were at the time of the original model creation.

The V-model is an improved version of the classic cascade model. V-shaped model is applicable to systems that are particularly important for smooth operation. Here at each stage, the current process is monitored to ensure that it is possible to move to the next level. In this model, testing begins from the stage of writing requirements, and for each subsequent stage provides its own level of test coverage.

For each level of testing, a separate test plan is developed, that is, during the testing of the current level, a testing strategy for the next one is being developed. When creating test plans, the expected test results are also determined and the input and output criteria for each stage are specified.

In the V-model, each stage of system design and development corresponds to a separate level of testing. Here the development process is represented by a descending sequence in the left part of the conditional letter V, and the testing stage is on its right edge. The correspondence of the stages of development and testing is shown by horizontal lines.

Stages of V-model methodology

The main steps of this methodology may vary, but they usually include the following:

1. Stage of requirements definition. Acceptance testing refers to this stage. Its main task is to assess the readiness of the system for the final use
2. The stage at which High-Level Design occurs. This phase refers to system testing and includes an assessment of compliance with the requirements for integrated systems
3. The Detailed Design phase is parallel to the integration testing phase, during which the interaction between various components of the system
4. After the stage of writing the code, another important step begins – unit testing. It is very important to make sure that the behavior of the individual parts and components of the software is correct and meets the requirements

Pros and cons of the V-model:

+ strict grading;

+ testing planning and system verification are carried out at early stages;

+ Improved, in comparison with the cascade model, time management;

+ intermediate testing.

– Insufficient flexibility of the model;

– The actual creation of the program occurs at the stage of writing the code, that is, already in the middle of the development process;

– insufficient risk analysis;

– There is no work with parallel events and the possibility of making dynamic changes.

When to use the V-model:

– In projects in which there are temporary and financial constraints;

– For tasks that involve a wider test coverage than the cascade model.