Rust TDD Workflow

What it does

When your agent uses it

• Implementing a new Rust function or feature test-first
• Fixing a Rust bug starting from a failing test
• Refactoring Rust code under test coverage
• Deciding how to test code that touches I/O or spawns commands

Example prompts

• “Add a function that truncates long strings in src/format.rs, test first.”
• “Fix the panic when parsing empty config input and add a regression test.”
• “Refactor the filter module without changing behavior, running cargo test after each step.”

Requirements

• A Rust project with cargo, rustfmt and clippy
• Pre-approved tools (allowed-tools): Read, Write, Edit, Bash

Workflow steps

3 steps, taken from the first numbered list in SKILL.md.

1. 1Do NOT write production code without a failing test
2. 2Write only enough test to fail (including compilation failure)
3. 3Write only enough production code to pass the failing test

What it can do on your machine

Read from SKILL.md and the folder at commit e4f0509. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves these tools, so the agent can use them without asking each time:

  • Read
  • Write
  • Edit
  • Bash

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • cargo

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  No URLs in SKILL.md.

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

Context cost

Rust TDD Workflow loads about 753 tokens when it runs, and up to ~1.6k if it reads all its reference files. Until then it costs about 62 tokens; SKILL.md has 215 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~62

When it runs · the whole SKILL.md, loaded when a task matches

~753

With references · SKILL.md plus every file in references/, read only if the agent opens them

~1.6k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

• NotePre-approves every shell command (allowed-tools: Bash)SKILL.md

  allowed-tools: Read, Write, Edit, Bash

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from rtk-ai/rtk at commit e4f0509, republished under its Apache-2.0 licence (© rtk-ai). 215 words, ~753 tokens.

name

rtk-tdd

description

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.

allowed-tools

Read, Write, Edit, Bash

effort

medium

tags

tdd, testing, rust, red-green-refactor, rtk

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)

test_{function}_{scenario}
test_{function}_{input_type}

cargo fmt --all --check
cargo clippy --all-targets
cargo test

© rtk-ai, Apache-2.0. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file (references) in .claude/skills/rtk-tdd of rtk-ai/rtk.

• SKILL.md
• references/testing-patterns.md

Open the folder on GitHubat commit e4f0509