Testing Models

There are various models which have been presented in the past 20 years in the field of Software Engineering for Development and Testing. Let us discuss and explore into few of the famous models. 

The following models are addressed: 

• Waterfall Model
• Spiral Model
• 'V' Model
• 'W' Model, and 

The Waterfall Model 

This is one of the first models of software development, presented by B.W.Boehm. The Waterfall model is a step-by-step method of achieving tasks. Using this model, one can get on to the next phase of development activity only after completing the current phase. Also one can go back only to the immediate previous phase.

In Waterfall Model each phase of the development activity is followed by the Verification and Validation activities. One phase is completed with the testing activities, then the team proceeds to the next phase. At any point of time, we can move only one step to the immediate previous phase. For example, one cannot move from the Testing phase to the Design phase. 

Waterfall Model 

Spiral Model 

In the Spiral Model, a cyclical and prototyping view of software development is shown. Test are explicitly mentioned (risk analysis, validation of requirements and of the development) and the test phase is divided into stages. The test activities include module, integration and acceptance tests. However, in this model the testing also follows the coding. The exception to this is that the test plan should be constructed after the design of the system. The spiral model also identifies no activities associated with the removal of defects. 

'V' Model

Many of the process models currently used can be more generally connected by the 'V' model where the 'V' describes the graphical arrangement of the individual phases. The 'V' is also a synonym for Verification and Validation.

By the ordering of activities in time sequence and with abstraction levels the connection between development and test activities becomes clear. Oppositely laying activities complement one another (i.e.) server as a base for test activities. For example, the system test is carried out on the basis of the results specification phase. 

The 'W' Model

From the testing point of view, all of the models are deficient in various ways:

• The Test activities first start after the implementation. The connection between the various test stages and the basis for the test is not clear.
• The tight link between test, debug and change tasks during the test phase is not clear.

Why 'W' Model? 

In the models presented above, there usually appears an unattractive task to be carried out after coding. In order to place testing on an equal footing, a second 'V' dedicated to testing is integrated into the model. Both 'V's put together give the 'W' of the 'W-Model'.