The Code Fairy (Fairy codices) is a species of Fairy, a creature that feeds off the belief of other species.
Evolution and Taxonomy
The modern Fairy species branched from its predecessor the Fairy radiant during the modern Pulp era, when the attitude towards broken devices changed from observe-theorize-repair-test-repeat to hit-until-works-or-hand-tired. This watering down of rigor enabled fairies to keep broken gadgets working for just a tad longer and feed off the belief of "I fixed it" until the device can no longer withstand the pressure and disintegrates. The Code Fairy is just one of a number of fairies that can infest Projects, for example the Fairy architecta can surface at an earlier age than the Code Fairy in an almost symbiotic relationship.
Biology and Defence
The Code Fairy is born out of the accumulated untested belief in a Project's (or Project facet's) absolute correctness, feeding off resources related to the Project such as Homo sapiens machinator ("I know this code works, I don't need to test it") and Homo sapiens architecta ("I know what the client means, I don't need to clarify it"). Perfectly working logic can show sudden glitches, unwanted consequences, illegal operations and in extreme cases, Abrupt Non-compilation Disorder (referred to as "...and?"). Specially trained "Testers" can detect the presence of Code Fairies; additionally Projects themselves can be inoculated by regular application of Test Driven Development. Code Fairies are classified as an introduced pest to most development ecosystems, so this is not viewed as ecological damage by the United Nations environmental task force.