Question

User acceptance testing in the V-Model

Software Quality, Software testing, Software testing and Quality Assurance (QA), Software testing models

In an V-Model approach when do you start writing the user acceptance testing test cases? In the BRS phase? At the end of system testing?

The v-model is essentially a modified waterfall SDLC, where planning and prep for some activities which occur late in the life-cycle actually take place earlier on. There are advantages and disadvantages to this SDLC, but to answer your question - UAT planning would most likely take place in the requirements analysis phase. See Wikipedia's V-model (software development) entry for a great diagram modeling this approach to software planning.

One big advantage to the V-model is that it engages test staff early in the cycle, preventing 'downtime' and employee turnover due to a feeling of disengagement. The biggest advantage to this slight modification of waterfall is that it allows testers to be active in the project early in the project's lifecycle. They develop critical knowledge about the system.

In my experience as a test manager for an extremely waterfall project spanning 13 workstreams and hundreds of testers, this early engagement is critical. Projects where 100% of the test organization is brought on 'just in time' tend to suffer from lack of experience and knowledge. Testers are prone to missing key defects because all they're doing is parroting back info they pulled from technical and functional specs which are months or even years old, out of date, and technically inaccurate.

The disadvantage to this approach, obviously, is that any changes to the plans will have double impact. Not only will requirements documents need to be updated, but so also will test documentation. If the system and solution are relatively stable, however, and if the company is married to the waterfall model, then this is a most efficient way to manage the project, and it's an effective way to maximize test effectiveness through early involvement.

All the best!

John Overbaugh is a testing professional with 13 years of experience. He blogs irregularly at http://thoughtsonqa.blogspot.com and is a frequent contributor and testing expert with IT Knowledge Exchange.
*************************************************
V-Model is same as waterfall as both follow sequential path of execution. Difference is that in V-Model there is more emphasis on testing. The test plan and cases are built quite in early stage before the actual development starts i.e. after the BRS is complete. It is useful for small projects as the development itself takes place in the implementation phase.