Hmmm.... googling around, there seems to be a lot of recent "programming koans" that are actually collections of rote exercises rather than lessons in zen enlightenment. Frustrating...
It looks like what happened was that a while back, someone made a very nice set of exercises each presented as a koan and a failing unit test to "meditate upon". Imitators then watered that down to exercises presented as failing unit tests to "meditate upon". Which was later watered down to just exercises...
For a classic example of an actual programming koan, I can only refer to the archive of Doug Bagely's "Functional Programming Koans, in OCaml" http://web.archive.org/web/20041012103936/http://www.bagley.... and, the old favorite teaching the relationship between objects and closures http://people.csail.mit.edu/gregs/ll1-discuss-archive-html/m...