# Rust workspace rules

## Test placement

- Never create a `tests.rs` (or `test.rs`) file under `src/`, and never `#[path = "tests.rs"] mod tests;`
- A test that reaches private items lives inline, in a `#[cfg(test)] mod tests { ... }` at the bottom of the file that owns those items
- A test that only uses the crate's public API lives in `crates/<crate>/tests/<subject>.rs`, next to `src/`
- Split a mixed test file along that line instead of widening visibility to move it
- A test for another crate's item belongs in that crate, not in a downstream one
- Never set `autotests = false` or hand-list `[[test]]` targets; every file directly under `tests/` is discovered by cargo, and a shared helper goes in `tests/<name>/mod.rs` or `tests/<subject>/support.rs` so it is not picked up as a test crate of its own