# Cost-effectiveness of testing

> XP applies two principles to improve cost-effectiveness of testing:

[XP](https://wiki.g15e.com/pages/Extreme%20programming.txt) applies two principles to improve cost-effectiveness of testing:

- [Double-checking (XP)](https://wiki.g15e.com/pages/Double-checking%20(XP.txt))
- [Defect cost increase](https://wiki.g15e.com/pages/Defect%20cost%20increase.txt)