In software development, 30 to 40 \% of all software activities are testing related. That is why it is critical to launch testing activities at the beginning of the project rather than after the coding is completed. While new software development models such as the Rational Unified Process and eXtreme Programming (XP) continue to be popular with practitioners, the V-model has gained particularly wide acceptance. Based on the V-model, this paper describes a model that shows how the tasks for testing relate to the tasks in the development model. This model - the W-model - further clarifies the priority of the tasks and the dependence between the development and testing activities. Although as simple as the V-model, the W-model makes the importance of testing and the ordering of the individual testing activities clear. It also clarifies that testing and debugging are not the same thing.