is a software development process
which can be presumed to be the extension of the waterfall model
. Instead of moving down in a linear way, the process steps are bent upwards after the coding
phase, to form the typical V shape. The V-Model demonstrates the relationships between each phase of the development life cycle and its associated phase of testing
The V-model deploys a well-structured method in which each phase can be implemented by the detailed documentation of the previous phase. Testing activities like test designing start at the beginning of the project well before coding and therefore saves a huge amount of the project time.
In the Requirements analysis
phase, the requirements
of the proposed system are collected by analyzing the needs of the user(s)
. This phase is concerned about establishing what the ideal system has to perform. However, it does not determine how the software will be designed or built. Usually, the users are interviewed and a document called the user requirements document is generated.
The user requirements document will typically describe the system’s functional, physical, interface, performance, data, security requirements etc as expected by the user. It is one which the business analysts use to communicate their understanding of the system back to the users. The users carefully review this document as this document would serve as the guideline for the system designers in the system design phase. The user acceptance tests are designed in this phase. See also Functional requirements, and Non-functional requirements''
is about system engineers analyze and understand the business of the proposed system by studying the user requirements document. They figure out possibilities and techniques by which the user requirements can be implemented. If any of the requirements are not feasible, the user is informed of the issue. A resolution is found and the user requirement document is edited accordingly.
The software specification document which serves as a blueprint for the development phase is generated. This document contains the general system organization, menu structures, data structures etc. It may also hold example business scenarios, sample windows, reports for the better understanding. Other technical documentation like entity diagrams, data dictionary will also be produced in this phase. The documents for system testing is prepared in this phase.
The phase of the design of computer architecture
and software architecture
can also be called as high-level design. The baseline in selecting the architecture is that it should realize all which typically consists of the list of modules, brief functionality of each module, their interface
, database tables
, architecture diagrams, technology details etc. The integration testing design is carried out in this phase.
The module design
phase can also be called as low-level design. The designed system is broken up in to smaller units or modules and each of them is explained so that the programmer can start coding directly.
The low level design document or program specifications will contain a detailed functional logic of the module
, in pseudocode
- database tables, with all elements, including their type and size - all interface details with complete API
references- all dependency issues- error message
listings- complete input and outputs for a module. The unit test design is developed in this stage.
In the V-model of software development, unit testing
implies the first stage of dynamic testing
process. According to software development expert Barry Boehm
, a fault discovered and corrected in the unit testing phase is more than a hundred times cheaper than if it is done after delivery to the customer.
It involves analysis of the written code with the intention of eliminating errors. It also verifies that the codes are efficient and adheres to the adopted coding standards. Testing is usually white box. It is done using the Unit test design prepared during the module design phase. This may be carried out by software testers, software developers or both.
In integration testing
the separate modules will be tested together to expose faults in the interfaces
and in the interaction between integrated components. Testing is usually black box
as the code is not directly checked for errors. It is done using the integration test design prepared during the architecture design phase. Integration testing is generally conducted by software testers.
will compare the system specifications against the actual system. The system test design is derived from the system design documents and is used in this phase. Sometimes system testing is automated
using testing tools.
Once all the modules are integrated several errors may arise. Testing done at this stage is called system testing.
- Roger S. Pressman:Software Engineering: A Practitioner's Approach, The McGraw-Hill Companies, ISBN 007301933X
- Mark Hoffman & Ted Beaumont: Application Development: Managing the Project Life Cycle, Mc Press, ISBN-10: 1883884454
- Boris Beizer: Software Testing Techniques. Second Edition, International Thomson Computer Press, 1990, ISBN 1-85032-880-3