I saw an interesting article on the pro’s and con’s of the waterfall model for software development at Builder AU. On the testing phase it states:
"Testing: In this stage, both individual components and the integrated whole are methodically verified to ensure that they are error-free and fully meet the requirements outlined in the first step. An independent quality assurance team defines “test cases” to evaluate whether the product fully or partially satisfies the requirements outlined in the first step. Three types of testing typically take place: unit testing of individual code modules; system testing of the integrated product; and acceptance testing, formally conducted by or on behalf of the customer. Defects, if found, are logged and feedback provided to the implementation team to enable correction. This is also the stage at which product documentation, such as a user manual, is prepared, reviewed and published."
It desribes the Pro’s as:
"First, the staged development cycle enforces discipline: every phase has a defined start and end point, and progress can be conclusively identified (through the use of milestones) by both vendor and client. The emphasis on requirements and design before writing a single line of code ensures minimal wastage of time and effort and reduces the risk of schedule slippage, or of customer expectations not being met.
Getting the requirements and design out of the way first also improves quality; it’s much easier to catch and correct possible flaws at the design stage than at the testing stage, after all the components have been integrated and tracking down specific errors is more complex. Finally, because the first two phases end in the production of a formal specification, the waterfall model can aid efficient knowledge transfer when team members are dispersed in different locations."
And it describes the Con's as:
"Despite the seemingly obvious advantages, the waterfall model has come in for a fair share of criticism in recent times. The most prominent criticism revolves around the fact that very often, customers don't really know what they want up-front; rather, what they want emerges out of repeated two-way interactions over the course of the project. In this situation, the waterfall model, with its emphasis on up-front requirements capture and design, is seen as somewhat unrealistic and unsuitable for the vagaries of the real world. Further, given the uncertain nature of customer needs, estimating time and costs with any degree of accuracy (as the model suggests) is often extremely difficult. In general, therefore, the model is recommended for use only in projects which are relatively stable and where customer needs can be clearly identified at an early stage.
Another criticism revolves around the model's implicit assumption that designs can be feasibly translated into real products; this sometimes runs into roadblocks when developers actually begin implementation. Often, designs that look feasible on paper turn out to be expensive or difficult in practice, requiring a re-design and hence destroying the clear distinctions between phases of the traditional waterfall model. Some criticisms also center on the fact that the waterfall model implies a clear division of labor between, say, "designers", "programmers" and "testers"; in reality, such a division of labor in most software firms is neither realistic nor efficient."