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Software Development Models - W-Model
Software Development Models
(Continued from previous question...)
Software Development Models - W-Model
From the view of testing, all of the models presented previously 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
In the following, the W-model is presented. This is based on the general V-model and the
disadvantages previously mentioned are removed.
The test process usually receives too little attention in the models presented and usually appears as
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 together give the “W” of the Wmodel.
Advantages of the W-Model
In the W-model the importance of the tests and the ordering of the individual activities for testing are
clear. Parallel to the development process, in a tighter sense, a further process - the test process - is
carried out. This is not first started after the development is complete.
The strict division between constructive tasks on the left-hand side and the more destructive tasks
on the right-hand side that exists in the V-model is done away with. In the W-model it is clear that such
a division between tasks is not sensible and that a closer co-operation between development and
testing activities must exist. From the project outset onwards the testers and the developers are
entrusted with tasks and are seen as an equal-rights partnership. During the test phase, the developer
is responsible for the removal of defects and the correction of the implementation. The early
collaboration and the tight co-operation between the two groups can often in practice avoid conflict
meetings.
The W-model becomes closer to practice when the test expenditure is given 40% and more. The
model clearly emphasises the fact that testing is more than just construction, execution and evaluation
of test cases.
Disadvantages of the W-Model
Models simplify the real facts. In practice there are more relations between the different parts of a
development process. However, there is a need for a simple model if all people involved in a project
are to accept it. This is also a reason why the simple V-model so frequently used in practice.
The models of software development presented do not clarify the expenditure needed for
resources that need to be assigned to the individual activities. Also in the W-model it appears that the
different activities have an equal requirement for resources (time, personnel, etc.) In practice this is
certainly not the case. In each project the most important aspects may vary and so therefore the
resource allocation is unlikely to be equal across activities. For highly critical applications the test
activities certainly have higher weighting or at least equal weighting with other activities.
(Continued on next question...)
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