# Rust Tests Guidelines

> Guidelines for writing Rust tests. Use this when you want to write Rust tests.

- Skill: `redisearch/rust-tests-guidelines` (Agent Skill)
- Install (CLI): `npx skillmds@latest add redisearch/rust-tests-guidelines`
- Raw SKILL.md: https://api.skillmd.com/api/skills/redisearch/rust-tests-guidelines/raw
- Safety review: pending
- Works with: Claude Code, Claude.ai, OpenAI Codex
- Category: Coding & Dev Tools
- Author: RediSearch (https://skillmd.com/u/redisearch)
- Updated: 2026-09-17
- Page: https://skillmd.com/skills/redisearch/rust-tests-guidelines

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# Guidelines for Writing Rust Tests

Guidelines for writing new tests for Rust code.

## Guidelines

1. Test against the public API of the code under test.
2. Test private APIs if and only if the private component is highly complex and difficult to test through the public API.
3. Use `insta` whenever you are testing output that is difficult to predict or compare.
4. Where appropriate, use `proptest` to add property-based tests for key invariants.
5. Testing code should be written with the same care reserved to production code.
   Avoid unnecessary duplication, introduce helpers to reduce boilerplate and ensure readability.
   The intent of a test should be obvious or, if not possible, clearly documented.
6. Do not reference exact line numbers in comments, as they may change over time.

## Code organization

1. Put tests for public (`pub`) items under the crate's `tests` directory. Two layouts are
   in use and both are fine — **match whichever the crate already has**:
   - **`tests/integration/`** — one test crate with its own `main.rs` and a module per
     area (`trie_rs`, `geo`, `query_eval`, …). Prefer this for a new crate: it compiles as
     a single unit instead of one binary per file.
   - **Cargo's default layout** — one integration binary per `tests/*.rs` file (`varint`,
     `fork_gc`, `rlookup`, …).
2. If the test *must* rely on private APIs, co-locate it with the code it tests, using a
   `#[cfg(test)]` module. Integration tests cannot reach `pub(crate)` or private items,
   so this is the only option for them — but prefer exercising the behavior through the
   public API where you can, per guideline 2 above.

## Dealing with extern C symbols

Check out [CONTRIBUTING.md](../../src/redisearch_rs/CONTRIBUTING.md) for instructions on how to deal with
undefined C symbols in Rust tests.