To make such a process work it is imperative that testers:
??? Focus on the earliest access to the requirements as they are assembled.
??? Get early access to prototype versions so they can prepare tests.
??? Provide review and possibly modeling feedback to management such that inconsistent or missing
requirements be identified asap.
4.4.4 Spiral Model (Figure 4.3)
The spiral model [Boehm 88] is based on the need to iterate. It contains as many iterations as are necessary
to bring a product to fruition. Each iteration requires that the participants plan, define their life-cycle,
prototype, analyze risks, write requirements, build models, detailed designs, code, unit, and system tests,
and install.
Story
ne test team identified by modeling that a check reader had to guess when the ???last???
check was in the tray.
This led to a small but crucial requirements change and avoided some major downstream
embarrassments. O
46
Manage Software Testing
The spiral model has a number of advantages:
??? It is flexible and allows for multiple iterations.
??? It employs prototyping extensively.
??? It allows for the coexistence of other models (indeed it expects candidate models to be proposed
and adopted if useful).
??? It makes risk evaluation explicit.
??? It acknowledges the need to validate requirements and design.
??? It was originally designed with a particular need to accommodate COTS, and is therefore more
amenable to software reuse.
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