Find Untested Sources (Polyglot)

Purpose

Coverage tools answer "which lines were executed?" — they require a green build and a passing test run, which is minutes-to-tens-of-minutes on a real repo. The question this skill answers is different and much cheaper:

Which source files have no test file referencing any of their declared symbols?

That's the question an agent asks before writing a new test — and it can be answered statically in a few seconds by parsing every recognized source file with tree-sitter, with no build, no dependency resolution, no compilation.

This is the polyglot sibling of the C# find-untested-sources skill. The output schema is intentionally compatible so the same prompt patterns can consume either tool.