This tiny ESLint plugin provides a single rule, `directory-mirror`, that enforces a one‑to‑one relationship between files in two directories (e.g., source files and their unit‑test counterparts). By configuring “mirrors” with source‑ and test‑folders, extensions, and recursion options, teams can automatically ensure that every file in one location has a matching file in the other, helping keep test coverage and project structure in sync.