- Corpus cases are blank-line-separated groups: program, JSON input, expected output lines. - `%%FAIL` cases require compile exit code `3`; runtime cases accept exit `0` or `5` with matching partial output. - Outputs are compared structurally as JSON; numeric `1` and `1.0` are equivalent. - Preserve output ordering, multiplicity, Unicode, compact one-value-per-line serialization, and special numeric behavior.