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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"oracle-gaps: a mutant of an owner under a config whose root is a subdirectory fails with setup-error","articleBody":"## Summary\n\nWhen a package's Vitest config sets `root` to a subdirectory, every mutant of an owner in that subdirectory fails with `setup-error`, and the report says `Cannot find module '/.oracle-gaps-\u003cpid>-\u003cn>-\u003cname>.property.test.mjs'`. The gap CLI's batch copy of the owner is resolved against the config root, not the package, so the copy's module id loses its directory.\n\n## Reproduction\n\nIn `packages/oracles`, with the repository's own `oracle-gaps/vitest.config.mjs` (its `root` is `dirname(import.meta.url)`, that is the `oracle-gaps/` directory):\n\n```sh\ncd packages/oracles\nnode oracle-gaps/index.mjs --package . --config oracle-gaps/vitest.config.mjs \\\n  --source oracle-gaps/contexts.mjs --only oracle-gaps/contexts.mjs:M1 --contexts 1 --out /tmp/gap-repro\n```\n\nOutput (abridged):\n\n```\noracle-gaps: gap setup-error L28 oracle-gaps/contexts.mjs:M1 ...\n  - Detail: Cannot find module '/.oracle-gaps-56182-1-gap-report-contexts-oracle.property.test.mjs'\n```\n\nEvery mutant of `contexts.mjs` fails the same way, so none is judged.\n\nDiagnosis: `runBatch` builds the copy path with `join(dirname(item.file), ...)`, and `item.file` is absolute and correct. The copy id that Vitest then loads is root-relative (`/…`), and the wrapper plugin's `resolveId` does not map it back. Changing only the config's `root` to the package directory (with `include: ['oracle-gaps/*.property.test.mjs']`) makes the same mutant run to a verdict (`crashed`, `TypeError: swap is not a function`), so the copy resolution is the cause.\n\n## Impact\n\nAny project whose Vitest config sets `root` to a subdirectory gets a setup-error for every mutant of an owner under that directory. The gap report judges none of them.\n\n## Notes\n\n- Not a test-only problem: it reproduces with the `--config` a user passes, not only the repo's own oracle-gaps config.\n- Workaround used for measurement only: a scratch config with `root` set to the package directory. Not merged.\n- Observed alongside: a run without `--only` runs every oracle file of the package, including the 30-minute e2e owner.\n\nFound while building the batch-runner oracle (TanStack/oracles, branch `test/oracle-gaps-batch-runner-r2`).\n","author":{"url":"https://github.com/KyleAMathews","@type":"Person","name":"KyleAMathews"},"datePublished":"2026-11-15T07:16:17Z","url":"https://github.com/TanStack/oracles/issues/101"}