Guide Rust development through test-driven development: write a failing test, implement enough code to pass, then refactor. Includes practical test patterns and final checks for formatting, static analysis, and test results.
Enforces TDD (Red-Green-Refactor) for Rust development. Auto-triggers on implementation, testing, refactoring, and bug fixing tasks. Provides Rust-idiomatic testing patterns with anyhow/thiserror, cfg(test), and Arrange-Act-Assert workflow.
Review the instructions the agent will receive before you install.
Cycle: RED (test fails) -> GREEN (minimum to pass) -> REFACTOR (cleanup, cargo test)
1. Write test in #[cfg(test)] mod tests of the SAME file
2. cargo test MODULE::tests::test_name -- must FAIL (red)
3. Implement the minimum in the function
4. cargo test MODULE::tests::test_name -- must PASS (green)
5. Refactor if needed, re-run cargo test (still green)
6. cargo fmt && cargo clippy --all-targets && cargo test (final gate)
Never skip step 2. If the test passes immediately, it tests nothing.
| Pattern | Usage | When |
|---|---|---|
| Arrange-Act-Assert | Base structure for every test | Always |
assert_eq! / assert! | Direct comparison / booleans | Deterministic values |
assert!(result.is_err()) | Error path testing | Invalid inputs |
Result<()> return type | Tests with ? operator | Fallible functions |
#[should_panic] | Expected panic | Invariants, preconditions |
tempfile::NamedTempFile | File/I/O tests | Filesystem-dependent code |
| Code Type | Test Pattern | Example |
|---|---|---|
| Pure function (str -> str) | Input literal -> assert output | assert_eq!(truncate("hello", 3), "...") |
| Parsing/filtering | Raw string -> filter -> contains/not-contains | assert!(filter(raw).contains("expected")) |
| Validation/security | Boundary inputs -> assert bool | assert!(!is_valid("../etc/passwd")) |
| Error handling | Bad input -> is_err() | assert!(parse("garbage").is_err()) |
| Struct/enum roundtrip | Construct -> serialize -> deserialize -> eq | assert_eq!(from_str(to_str(x)), x) |
test_{function}_{scenario}
test_{function}_{input_type}
Examples: test_truncate_edge_case, test_parse_invalid_input, test_filter_empty_string
Command::new() -> test the parser, not the executionstd::process::exit() -> refactor to Result first, then test the Resultcargo fmt --all --check
cargo clippy --all-targets
cargo test
All 3 must pass. No exceptions. No #[allow(...)] without documented justification.
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Simplify Rust code in RTK by replacing verbose loops, unnecessary copies, and excessive abstractions with common Rust patterns. Preserve behavior and project requirements, including error context, fallback handling, exit codes, and existing test modules.
Choose Rust design patterns for RTK modules that process command output. Use concrete examples to structure configuration, prevent type mixups, manage parser states, and select abstractions suited to the task without adding unnecessary architectural complexity.
Organize open GitHub issues by category, risk, linked pull requests, duplicate candidates, and inactivity. Optionally analyze selected issues in depth, draft responses, and apply approved comments, labels, or closures to keep the backlog actionable.
Sort open GitHub pull requests by change size, automated check results, conflicts, and inactivity. Review selected changes in detail, draft constructive feedback, and post comments after the user approves them.
Review GitHub issues and pull requests together to find duplicate work, security findings without fixes, and critical bugs without linked changes. Produce action tables and a dated report to support backlog reviews and sprint planning.
Develop Rust filters for RTK through tests written before implementation. Use real command output as test inputs, check output snapshots and unexpected inputs, verify a minimum reduction target, and complete formatting, linting, and test checks before finishing.