At MongoDB we write open source database drivers in ten programming languages. We also help developers in our community replicate our drivers' behavior in even more (and more exotic) languages. Ideally, all drivers behave alike; or, where they differ, the differences are written down and justified. How can we herd all these cats along the same path?
For years we failed. Each false start at standardization left us more discouraged. But we’ve recently gained momentum on standardizing our drivers. Human-readable, machine-testable specs, coded in YAML, prove which code conforms and which does not. These YAML tests are the Cat-Herd's Crook: a tool to guide us all in the same direction.