Interesting quote from a piece over at Software Development Times:
We realized that testing in a lab behind a firewall is kind of ridiculous in the web era. You can’t replicate the Internet behind the firewall. Add in dependencies on third-party services and it’s impossible. The only real true way of testing today is in production. Seventy percent of our load testing is done in production right now.
Building production-like testing environments is a complex process and depending on the application is more work than its worth, both in time and dollars.