Defect leakage (escape) is a true mirror of test effectiveness. Internal defect escapes enable us to understand the quality of tests during the development and if done well can act as a rapid effective feedback loop to strengthen testing and deliver superior products/applications. External escapes i.e. field defects are very useful to improving system tests by understanding fine points of deployment and usage. Watch this video to understand how to measure escapes, classify, set up feedback loops and improve.