Rust testing

Purpose

Generic cargo/nextest unit-test conventions for rust-stack projects. Prefer the repo's TEST_CMD from AGENTS.md when it is more specific.

When to Use

• Adding or changing crate-level Rust tests.
• Choosing cargo test vs cargo nextest run.
• Placing tests beside a module or under tests/.

Do not use this skill for product-specific GUI, TUI, or integration harnesses. Those belong in repo-local skills.

Required Tools

• cargo
• cargo nextest when nextest.toml or .config/nextest.toml exists
• The project TEST_CMD from AGENTS.md

Workflow

1. Read AGENTS.md for the canonical test command. If nextest.toml exists, prefer cargo nextest run; otherwise cargo test.
2. Put unit tests next to the module (*_tests.rs or an inline #[cfg(test)] module) unless the crate already uses tests/ integration tests.
3. Run the narrowest command first (cargo test <name> or cargo nextest run -E 'test(<name>)').
4. Keep one behavior per test; cover error paths, not only the happy path.

Agent-Safe Patterns

• Do not disable or weaken tests to go green.
• Do not run workspace-wide test suites when a single crate or filter is enough.
• Format/clippy stay on the lint skill (cargo fmt --check, cargo clippy).

Verification Checklist

• Used the repo TEST_CMD or a documented subset
• Targeted test failed for the intended reason before the fix (when adding coverage)
• Targeted test passed after the change

Resolve helper paths from this skill directory. Run project commands from the target workspace.