tdd

A command that enforces test-driven development, or TDD: write a test that fails, add only enough code to pass it, then improve the result.

In plain words
What is it for?
Use it to create shell tests with BATS or Python tests with pytest for a feature, with options for the test language and file path.
Why use it?
It prevents production code from being written before its expected behaviour is captured in a failing test.

Command for Claude Code

Install

Getting it into your agent

One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.

agentmods
npx agentmods add commands/osmantic/ods/tdd
Clone the repo
git clone --depth 1 https://github.com/Osmantic/ODS

Made for: Claude Code.

Per session 17 Only the description is in the session, so the agent can decide to use it. The body loads when it is invoked.
When invoked 3,625 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5 $0.00017 $0.03625
Opus 5 $0.00009 $0.01813
Sonnet 5 $0.00003 $0.00725
Haiku 4.5 $0.00002 $0.00363

Measured 2d ago against content hash 9dcee87bf9ba, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

tdd scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.claude/commands/tdd.md · 509 lines

How it starts

The opening of the file, as written. The whole thing — 509 lines — stays where its author put it; the contents beside it link to each section on GitHub.

TDD TDD TDD - Strict Test-Driven Development

Enforce the classic Red -> Green -> Refactor cycle. Tests are written FIRST, implementation comes SECOND.

"TDD TDD TDD" - the repetition is intentional. This skill enforces discipline.

ODS has two test ecosystems: Shell (BATS + bash assert) and Python (pytest). This skill handles both.

Arguments

  • $ARGUMENTS - Feature description and options:
    • First part: Feature description in quotes or as text
    • --shell - Write shell/BATS test (default for installers/, scripts/, ods-cli)
    • --python - Write Python/pytest test (default for dashboard-api/)
    • --file <path> - Explicit test file path

The Three Laws of TDD

  1. You may not write production code until you have written a failing test
  2. You may not write more test than is sufficient to fail
  3. You may not write more production code than is sufficient to pass the test

Philosophy: Ask Early, Ask Often

This skill should liberally use AskUserQuestion at decision points. TDD involves judgment about what to test, test granularity, and when the implementation is "done." The user should direct these choices.

  • Before writing the test — confirm what behavior to test and test type
  • After RED phase — validate that the failure is the right kind before implementing
  • After GREEN phase — ask if the implementation approach is acceptable
  • After each cycle — ask whether to iterate or stop

Workflow

Phase 0: Understand the Feature

Before writing anything:

  1. Parse $ARGUMENTS to extract feature description and flags
  2. Analyze the feature - what behavior needs to be tested?
  3. Determine test ecosystem (Shell or Python) based on the feature area:
Shell Test Locations (BATS)
Feature Area Test Path Implementation Path
Installer libraries tests/bats-tests/<lib>.bats installers/lib/<lib>.sh
Installer phases tests/bats-tests/<phase>.bats installers/phases/<phase>.sh
Scripts tests/test-<script>.sh scripts/<script>.sh
CLI features tests/test-<feature>.sh ods-cli
Compose selection tests/bats-tests/compose-select.bats installers/lib/compose-select.sh

Read the full file on GitHub · 509 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago First seen · 509 lines · 17 tokens per session scan A 9dcee87bf9ba

Subscribe to this mod's changes

tdd is a command published in the GitHub repository Osmantic/ODS (5,819 stars, last pushed yesterday), licensed Apache-2.0. It adds 17 tokens to every session and 3,625 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.