Testing Models - Understanding V-Model from testing perspective

V-Model is a software development  Model which shows software development life cycle to follow a V shape. V-Model was developed with the intention to cover some of the problems found in waterfall Model with one of the main issue as defect uncovered late in the Software development life cycle.

The main purpose of representing in a V is to show the relationship between each phase of development life cycle with its associated phase in testing. The execution of processes happens in a sequential manner in this model. This is also sometimes called as Verification and Validation Model

During the initial stage, i.e. from requirement to Coding and Implementation are verification phase and then from Coding and Implementation to User Acceptance testing are Validation phases in the model.

Before continuing with understanding the responsibility of testing in various phases of a V-Model, we must distinguish between Verification and Validation.

Objective of Verification is to ensure the product is being built according to requirement .Walk-through, reviews, inspection are some of the activities, whereas objective of Validation is to ensure the product build meets the user requirement. Whereas Verification activities are mostly done during product building process, Validation is done post product is build

Below are the activities performed by testing team during various stages of V-Model.

a. Requirement Analysis

 Testing tasks includes preparation of User Acceptance testing plan to be followed during UAT testing during the first phase of V-Model. Involvement of testing team early in the requirement help understanding the requirement and analyzing gaps and refining requirements based on scenarios identified for User Acceptance testing.   

b. System Design

 Once we have the requirement signed off by the customer, the developer and testers in parallel starts to work on system development design and system test design respectively.

c. Architecture Design

In this phase, test and plans related to integration testing of different modules are created. From development point of view, In this phase, high level design of the system is created starting from dividing requirement into different modules based on functionality and the interaction of modules defined with each other , external world as well as existing modules if the new functionality is an added functionality in the existing system.

d. Module Design

This phase from development point of view defines the low level design of each of the modules.  To ensure each module is working correctly, to test the internal structure of the module, we need to create unit test cases to test units in the module. Unit testing is mostly performed by developers as is mostly related to internal structure and design of modules.
   

e. Coding and Implementation

Next Phase in the V-model is implementation of low level design into code. So in all the above phases of the V-Model, similar to developers, testing phases occurs in parallel and does verification and analysis at each phase and prepares for testing.

f. Unit Testing 

 Once Coding and Implementation is completed, we need to execute unit test to verify the designed has been coded and implemented properly. Units are tested as they are developed. Unit tests prepared during Module designed are executed to unit test the modules individually

g. Integration Testing

Once the modules are unit tested individually, it is the time to test integration of modules with other modules and external systems. Integration test prepared during Architecture design are executed in this phase.

h. System Testing

 Once we have tested the modules followed by Integration of modules and external systems. Next step is to verify whether the system is working properly and as defined in the requirements
    

i. Acceptance Testing

 Once the system is tested properly by QA Team, it is passed on to customer to perform User acceptance test. This can be performed by client or UAT Team designated by client.Please note from  step f. on wards, we started in step a. to e., the necessary test preparation and analysis tasks.
  

Conclusion  On a whole, V-Model is a much disciplined Model with salient feature including testing starting as early as possible from requirement phase. Requirements are clear and properly analyzed by different perspective, i.e. business analysts, testers and developers. This model has shortcomings in case of some requirement changes in between the software development life cycle