On the 3rd hand, a major aspect of the 'engineering' part of being a 'software engineer' is learning how to choose which side of various tradeoffs is appropriate for a project. Should we perform the expensive computation on demand at runtime, or is trading time for space with a lookup table more appropriate? Is the task simple enough for a basic 'glue language' like bash, or does it require a full-featured language like ruby or python?

Regardless, as you pointed out, regardless of the language some sort of testing is still a good idea. Even small, supposedly 'trivial' scripts deserve some testing!