Whatever the phase,learn from the problem and institute measures to improve it.
Preventing a defect from being released into production is to test for it.This is not an improvement in real sense. Preventing a defect means keeping it from coming into existence, not finding afterwards.
because it is far more expensive to find defect at each later stages.
Hence defect prevention is about theentire development life cycle.
by keeping track of post-release defects as well as their root causes you cannot only measure the efficacy of your development and test processes but also improve them.
The development of high-quality software is an essential business activity in many organizations. Improving software quality requires the effective use of a software development process with well-defined phases of development and a metrics program to define and verify product and process quality. A key objective in software development is phase containment of defects.i like it very much and also very useful for me. I got various "Quality Testing" Resource from macrotesting http://www.macrotesting.com