The facility of Ruby on Rails' test, development and production environments is one of those features that goes almost unremarked, but which makes using rails more pleasant. No doubt everyone has their own solution for this in other environments, and while I am sure Common Lisp is not lacking in examples, I have not seen an idiomatic implementation. In developing cl-blog-generator I came up with the following solution.
Today's surprise was that "2009-01-01" and "2009-1-1" get parsed differently by the YAML parser in Rails. The former gets converted to a Date, while the latter becomes a String. It confused me for a while, as the problem only showed up when I wanted to send the dates to a Flot chart. Looking at the standard, it's conforming behaviour. Must be me that is non-conforming then...