Testing is a process used for revealing defects in s/w and for establishing that the s/w has attained a specific degree of quality.
The s/w testing group’s main objective is to ensure that the s/w is doing what it is supposed to do as well as the s/w is not doing what it is not supposed to do. With this objective, it is clear that it is necessary to have a separate group for testing the s/w other than the group which developed it.
Also, bugs in the s/w can cause severe monetary as well as other loss to the organization. So it is important to allocate some budget for the testing group.