The helper's own contract — marker handling, requested position, label
extraction and the rejection when the marker is absent — is asserted against
in-memory documents whose contextual types are written inline, so the helper
is tested without coupling to the library's code.
src/util/__tests__/ holds shared test helpers, reached from anywhere
in the source tree as `#test-utils/<name>.ts` through
package.json#imports. A bare `~/…` is not a valid imports key — Node
requires `#` — and a direction-free specifier keeps
import/no-relative-parent-imports from ever firing. The `__tests__`
folder name is the pattern tsconfig.build.json already excludes, so
helpers can never ship. Lint scoping: import/no-nodejs-modules off for
the folder (the probe spawns a language server) and
typescript/promise-function-async off to match its promise-returning
style. The LSP probe moves in from scripts/; a smoke test pins the
specifier's resolution and typing without starting a server.
tmu