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.
npx agentmods add skills/outlinedriven/odin-codex-plugin/test-drivennpx skills add OutlineDriven/odin-codex-plugin --skill test-drivengit clone --depth 1 https://github.com/OutlineDriven/odin-codex-pluginWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00038 | $0.01248 |
| Opus 5 | $0.00019 | $0.00624 |
| Sonnet 5 | $0.00008 | $0.00250 |
| Haiku 4.5 | $0.00004 | $0.00125 |
Grade A, and why
test-driven 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.
Copies of this mod
1 near-identical copy found in the catalogue:
- test-driven — 95% identical, 2 lines differ
How it starts
The opening of the file, as written. The whole thing — 114 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-driven development (XP-style)
Tests define the specification. Design them from requirements before any implementation. The RED-GREEN-REFACTOR cycle is the heartbeat: write a failing test, make it pass with minimal code, then clean up while green.
Modern insight (2025): TDD + property-based testing pairing is the standard -- example tests prevent regressions, property tests discover edge cases. TDD also serves AI-assisted development: structural integrity keeps code understandable for both human and AI collaborators (Kent Beck, "Augmented Coding"). Mutation testing validates test quality beyond coverage metrics (TDD+Mutation: 63.3% vs TDD-alone: 39.4% mutation coverage).
See frameworks for language-specific test runners, property testing, coverage, and mutation tools. See examples for brief TDD cycle patterns per language.
When to Apply
- New features with clear requirements (both inside-out and outside-in approaches valid)
- Bug fixes -- write a failing test that proves the bug before fixing
- Refactoring -- ensure coverage exists before restructuring
- API contract enforcement -- test the interface, not internals
- Property-based invariants -- complement example tests with PBT
- Legacy code -- add characterization tests before modifying (Michael Feathers pattern)
When NOT to Apply
- Exploratory prototyping or spike research
- One-off scripts, data migrations, generated code
- Purely visual UI layout work (prefer visual regression testing)
- Highly experimental algorithmic research (but PBT still helps)
- Throwaway code with <1 week lifespan
Anti-patterns
- Test-last: Writing tests after implementation defeats the design benefit
- Testing implementation details: Tests should verify behavior, not internal structure -- breaks refactoring confidence
- Over-mocking: Testing the mocks instead of the code; mock external I/O, not core logic
- Skipping RED: Tests that never fail aren't tests -- they verify nothing
- 100% coverage obsession: Coverage does not equal quality. Mutation testing exposes gaps coverage cannot
- Refactoring on RED: Never restructure with failing tests
- Test-induced architectural damage: Letting mock boundaries dictate design
- Snapshot bloat: Approval-style tests without curation become maintenance burden
What ships with it
7 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 2d ago First seen · 114 lines · 38 tokens per session scan A c2092a85c429
test-driven is a skill published in the GitHub repository OutlineDriven/odin-codex-plugin (15 stars, last pushed 1mo ago), licensed Apache-2.0. It adds 38 tokens to every session and 1,248 once invoked, about $0.0002 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.
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