[afterburner5]

I worked for a company at some point where, due to the how the original product was built, testing before a release took between 3 and 5 days and was generally quite brittle.

Within my first three months there, we had business requests to improve that. Invariants, and generally speaking, contracts for our models helped us out. Because we were able to run effective, cheap, fast tests, that proved our implementations were satisfying our requirements, pre and post conditions, invariants, the whole shebang, at the contract level, without even worrying about the actual underlying implementation.

This greatly simplified the release tests, and it meant we were able to release much quicker, and with a higher confidence than before