Environment parity is the ideal state where the various environments in which code is executed behave equivalently. The lack of environment parity is one of the more frustrating and tenacious aspects of software development. Deployments and development both fall victim to this pitfall too often, reducing stability, predictability, and productivity. When parity is not achieved, environments behave differently, which makes troubleshooting hard and can make collaboration seem impossible. This lack of parity is a burden for too many developers and operational staff. Looking back on almost every problem I have seen in new production deployments, I find it hard to think of one issue that wasn't due in some part to lack of parity. For developers, this pain is felt when integrating and testing code.