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Agent skill

Develop TDD

by danielvm-git in danielvm-git/bigpowers

Test-driven development with red-green-refactor loop using vertical slices.

MITAuto-check passedTesting & QA

Install Develop TDD

skills CLI
$ npx skills add danielvm-git/bigpowers --skill develop-tdd -a claude-code

Project install by default; add -g for ~/.claude/skills/.

GitHub CLI
$ gh skill install danielvm-git/bigpowers develop-tdd --agent claude-code

Project scope by default; add --scope user for a personal install. Needs GitHub CLI 2.90.0 or later (public preview).

Manual copy
$ git clone --depth 1 https://github.com/danielvm-git/bigpowers.git skills-src && mkdir -p .claude/skills && cp -r skills-src/skills/develop-tdd .claude/skills/develop-tdd && rm -rf skills-src

Use ~/.claude/skills/ instead of .claude/skills for a personal install. The folder must contain SKILL.md.

Claude Code skills documentation · loads skills from .claude/skills/

Facts

Skill name
develop-tdd
GitHub stars
257
Token cost
~1.7k tokens
SKILL.md length
723 words
Files
7
Skills in repo
39
Repo updated
First seen
Licence
MIT

At a glance

Test-driven development with red-green-refactor loop using vertical slices.

  • Works in 7 steps: Planning → Tracer Bullet → Incremental Loop → …
  • Features (epic tasks)
  • SKILL.md covers Philosophy, Red Flags, Workflow and Checklist Per Cycle, plus 3 more sections
  • Calls bash and git

What it does

Develop TDD is an agent skill from danielvm-git/bigpowers. Test-driven development with red-green-refactor loop using vertical slices. Use for features (epic tasks) or bugs (specs/bugs/BUG-.md).

Its SKILL.md is about 1.7k tokens, which your agent loads only when the skill is triggered. The skill folder holds 6 other files (for example `REFERENCE.md`, `deep-modules.md` and `interface-design.md`).

It sits in Testing & QA, covering Test-driven development. The repository describes itself as: Agent skills synthesizing years of software engineering discipline into a prescriptive methodology for solo developers. The licence is MIT.

When your agent uses it

  • Features (epic tasks)
  • Bugs (specs/bugs/BUG-.md)

Example prompts

  • “/develop-tdd”

Workflow steps

7 steps, taken from the step headings in SKILL.md.

  1. Planning
  2. Tracer Bullet
  3. Incremental Loop
  4. Visual Slices (UI alternate workflow)
  5. Refactor
  6. Verify
  7. Manual Verification Handover

What it can do on your machine

Read from SKILL.md and the folder at commit 812d57a. It shows what the files ask for, not the result of running them.

  • Tool permissions

    Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

    From allowed-tools in the SKILL.md frontmatter.

  • Runs code

    Shell commands in SKILL.md call:

    • bash
    • git

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

  • Network

    No URLs in SKILL.md. Its commands use git, which can reach the network depending on how they are called.

    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

Develop TDD loads about 1.7k tokens when it runs. Until then it costs about 37 tokens; SKILL.md has 723 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it
~37
When it runs · the whole SKILL.md, loaded when a task matches
~1.7k

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

Auto-check passed

The automated check found no risky patterns in SKILL.md.

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 danielvm-git/bigpowers at commit 812d57a, republished under its MIT licence (© danielvm-git). 723 words, ~1,722 tokens.

Download SKILL.mdSave it as .claude/skills/develop-tdd/SKILL.md (or your agent's skills folder). This skill also uses 6 other files; get the full folder from GitHub.
name
develop-tdd
description
Test-driven development with red-green-refactor loop using vertical slices. Use for features (epic tasks) or bugs (specs/bugs/BUG-*.md).
model
sonnet
effort
standard

Develop TDD

HARD GATE — Do NOT proceed if on main or master. Run kickoff-branch first to create a feature branch or worktree.

HARD GATE — Do NOT write code before you have a plan. New feature: plan-work → epic capsule tasks. Bug: investigate-bug → specs/bugs/BUG-*.md (or use fix-bug orchestrator).

RECURSIVE DISCIPLINE — This lifecycle applies to EVERY task, including updating these skills. Never skip planning because a task is "meta" or "just documentation."

Philosophy

Tests verify behavior through public interfaces, not implementation details. A good test reads like a specification. See REFERENCE.md for the horizontal-slice anti-pattern and TDD phase detail.

Red Flags

If you catch yourself thinking these, stop and reconsider — you are likely deviating from production-grade craft.

Red FlagReality
"This is too simple to need tests."Simple code is where bugs hide. If it's simple, the test is cheap.
"I'll refactor this later.""Later" is when technical debt becomes bankruptcy. Refactor while Green.
"The tests are already comprehensive."If you're adding behavior, you need a new test. Coverage ≠ Correctness.
"I'm just fixing a small bug."Small bugs often indicate deep interface flaws. Investigate root cause.
"I need to mock this internal class."Mocking internals couples tests to implementation. Mock only I/O.
"This refactor is out of scope."Leave the code cleaner than you found it (Boy Scout Rule).
"Preflight failed but it's unrelated."Always Green: any reproducible gate failure routes quick-fix → fix-bug before forward work. Session boundaries do not waive Preflight.
"I'll note the red gate and continue."Narrating a failure is banned. fix-or-log is mandatory per CONVENTIONS § Discovered Defects.

Workflow

Timing: bash scripts/bp-timing.sh start develop-tdd at invocation; bash scripts/bp-timing.sh end develop-tdd before handoff.

1. Planning
  • Read active specs/epics/*/epic.yaml story tasks or specs/bugs/BUG-*.md — understand verify steps
  • If specs/tech-architecture/eNN-TEST_PLAN_LATEST.md exists for the active epic, read it before writing the first test. Implement P0 scenarios (SC-*-P0-*) before P1. P2/P3 scenarios are optional per time budget.
  • Confirm interface changes and behaviors to test (prioritize)
  • Design interfaces for testability — identify deep modules opportunities
  • Get user approval on the plan

Apply the enforce-first F.I.R.S.T rubric: Fast, Independent, Repeatable, Self-Validating, Timely.

2. Tracer Bullet

Write ONE test that confirms ONE thing about the system:

RED:    Write test for first behavior → test fails → commit: test(<scope>): ...  (test-only; red in CI)
GREEN:  Write minimal code to pass → test passes → commit: feat(<scope>): ...   (fix commit; green)
REFACTOR (optional): clean up → commit: refactor(<scope>): ...

Two-commit red/green policy (HARD GATE — e45s08) — Each behavior cycle requires two separate commits: (1) test-only commit that fails in CI (RED), then (2) implementation commit that makes it pass (GREEN). Never combine test + fix in one commit. Before proceeding, run the mechanical RED isolation check:

bash
bash scripts/verify-tdd-red-commit.sh

Show git log -2 --oneline and the script output as evidence. If the test-only commit passes in isolation, the RED gate is violated — stop and fix before GREEN.

tasks.yaml ledger (e45s06) — After each task's verify: exits 0, update eNNsYY-tasks.yaml: set that task's status: passing. Story-level status: passing only when all tasks pass.

Show full SKILL.md (272 more words)Show less
3. Incremental Loop

Snapshot-before-transition (e45s34): Before each RED → GREEN or GREEN → REFACTOR transition, create a checkpoint so a failed transition can be rolled back cleanly:

bash
bash scripts/bp-yaml-snapshot.sh specs/state.yaml   # if state changed this cycle
git stash push -m "tdd-checkpoint-$(git rev-parse --short HEAD)-red" --keep-index 2>/dev/null || true

After GREEN passes and is committed, drop the stash (git stash drop if empty). Never refactor while RED.

For each remaining behavior: RED → GREEN → REFACTOR (optional). One test at a time. Two commits per behavior (test-only RED, then fix GREEN). Commit after every GREEN phase.

4. Visual Slices (UI alternate workflow)

For UI components where behavioral unit testing is brittle: extract logic into a Controller/ViewModel/Hook (pure TDD), then use Visual Slices for the View layer. See REFERENCE.md for the full Visual Slices procedure.

5. Refactor

After all tests pass: extract duplication, deepen modules, apply SOLID principles. Never refactor while RED.

6. Verify

After every behavior cycle, run the verify command from the active epic task. Show evidence before declaring the step done.

7. Manual Verification Handover

Once all tests pass: locate the Verification Script in the active epic capsule, present it to the user step-by-step, and wait for confirmation of behavioral correctness.

6a. CI dry-run sub-step

If this cycle modified files in .github/workflows/, run the CI dry-run procedure documented in REFERENCE.md.

Checklist Per Cycle

[ ] Test describes behavior, not implementation
[ ] No test is ignored without an explicit ambiguity note (T4)
[ ] Boundary conditions tested: empty, max, min, off-by-one (T5)
[ ] Tests verify behavior through public interface only — no private methods (T8)
[ ] Test would survive internal refactor
[ ] Code is minimal for this test
[ ] No speculative features added
[ ] Every new abstraction has an explicit "Reason for Depth" justification
[ ] Progress committed (Conventional Commits)
[ ] verify: command passes

Handoff

Gate: READY -> next: verify-work Writes: state.yaml handoff.next_skill = verify-work

BCP Plus Integration

At story completion, if the story was sized with BCP Plus (13-dimension breakdown), log the bcp_plus.total alongside the standard bcps: count in the story's tasks.yaml. The breakdown is available from the epic capsule's bcp_plus_breakdown field. See docs/references/bcp-plus.md for the full methodology and NFR Gate pattern.

Verify

→ verify: test -x scripts/verify-tdd-red-commit.sh && bash scripts/verify-tdd-red-commit.sh --self-test && grep -q 'verify-tdd-red-commit' skills/develop-tdd/SKILL.md && echo OK

<!-- story: e02s04 -->

© danielvm-git, MIT. 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 6 other files in skills/develop-tdd of danielvm-git/bigpowers.

  • SKILL.md
  • REFERENCE.md
  • deep-modules.md
  • interface-design.md
  • mocking.md
  • refactoring.md
  • tests.md

Open the folder on GitHubat commit 812d57a

Compare with similar skills

Develop TDD next to the 5 skills that share the most tags, products or categories with it. Stars are the repository's; “used in” counts other GitHub owners with a copy.

Develop TDD compared with similar skills
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Develop TDD this skilldanielvm-git/bigpowers257—~1.7kAutomated safety check: PassMIT
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TDD WorkflowhellangleZ/burn-in-cceverywhere-ralph11211 repos~2.4kAutomated safety check: PassNone
TDDsanity-io/sanity6.4k20 repos~1kAutomated safety check: PassMIT
Test Driven Developmentfarm-fe/farm5.6k51 repos~2.5kAutomated safety check: PassMIT
Tapd Story PipelineTencentBlueKing/bk-bcs840—~2.6kAutomated safety check: PassCustom licence

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Categories

Questions about Develop TDD

What does Develop TDD do?

Test-driven development with red-green-refactor loop using vertical slices. Develop TDD is an agent skill from danielvm-git/bigpowers. Test-driven development with red-green-refactor loop using vertical slices.

When should I use Develop TDD?

Develop TDD fits situations like: features (epic tasks); bugs (specs/bugs/BUG-.md).

How do I install Develop TDD in Claude Code?

Run `npx skills add danielvm-git/bigpowers --skill develop-tdd -a claude-code`. Or copy the skill folder (skills/develop-tdd in danielvm-git/bigpowers) into .claude/skills/develop-tdd in your project. Claude Code loads it when a task matches its description.

How do I install Develop TDD in Codex?

Run `npx skills add danielvm-git/bigpowers --skill develop-tdd -a codex`. Or copy the skill folder (skills/develop-tdd in danielvm-git/bigpowers) into .agents/skills/develop-tdd in your project. Codex loads it when a task matches its description.

Can I use Develop TDD in Cursor, Gemini CLI or GitHub Copilot?

Cursor, Gemini CLI, GitHub Copilot and OpenCode also load SKILL.md folders. With the skills CLI, run `npx skills add danielvm-git/bigpowers --skill develop-tdd -a cursor` (or -a gemini-cli, github-copilot or opencode for the others). To copy it by hand, put the folder in .cursor/skills/develop-tdd, .gemini/skills/develop-tdd, .github/skills/develop-tdd and .opencode/skills/develop-tdd in your project.

What does Develop TDD need to run?

Going by SKILL.md and its folder, Develop TDD needs the command-line tools its instructions call (bash and git).

Does Develop TDD access the network?

SKILL.md contains no URLs. Its commands use git, which can reach the network depending on how they are called. This is read from the text; nothing was executed.

Is Develop TDD safe to install?

Our automated static check of SKILL.md found no risky patterns, such as piping downloads into a shell, reading credential files or hidden Unicode. It is not a guarantee. Review the folder before installing.

What licence does Develop TDD use?

Develop TDD is published under the MIT licence (the repository's licence). It allows redistribution, so the full SKILL.md is shown on this page.

How many tokens does Develop TDD use?

About 1.7k tokens (SKILL.md is roughly 6.9k characters). Agents keep only the skill's name and description in context until a task matches; then they load SKILL.md in full.

What are the alternatives to Develop TDD?

Skills that share tags, products or a category with Develop TDD: TDD (pietheinstrengholt/rssmonster, 564 stars), TDD Workflow (hellangleZ/burn-in-cceverywhere-ralph, 112 stars), TDD (sanity-io/sanity, 6.4k stars) and Test Driven Development (farm-fe/farm, 5.6k stars). The comparison table on this page puts their stars, adoption, token cost, safety result and licence side by side.

Who maintains Develop TDD?

danielvm-git (a GitHub user) maintains it in danielvm-git/bigpowers, which has 257 GitHub stars. The repository holds 39 skills in this directory. The repository was last updated on September 21, 2026.

Source: danielvm-git/bigpowers on GitHub. Facts on this page come from the repository at the commit we read; the author's words are quoted as theirs.