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 skills add summarybotng/summarybot-ng --skill tdd-london-chicagogit clone --depth 1 https://github.com/summarybotng/summarybot-ngWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/summarybotng/summarybot-ng/tdd-london-chicago)<a href="https://agentmods.dev/skills/summarybotng/summarybot-ng/tdd-london-chicago"><img src="https://agentmods.dev/badge/skills/summarybotng/summarybot-ng/tdd-london-chicago/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/summarybotng/summarybot-ng/tdd-london-chicago"><img src="https://agentmods.dev/badge/skills/summarybotng/summarybot-ng/tdd-london-chicago.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00037 | $0.01740 |
| Opus 5 | $0.00018 | $0.00870 |
| Sonnet 5 | $0.00007 | $0.00348 |
| Haiku 4.5 | $0.00004 | $0.00174 |
Grade A, and why
tdd-london-chicago 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 250 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Test-Driven Development: London & Chicago Schools
<default_to_action> When implementing TDD or choosing testing style:
- IDENTIFY code type: domain logic → Chicago, external deps → London
- WRITE failing test first (Red phase)
- IMPLEMENT minimal code to pass (Green phase)
- REFACTOR while keeping tests green (Refactor phase)
- REPEAT cycle for next functionality
Quick Style Selection:
- Pure functions/calculations → Chicago (real objects, state verification)
- Controllers/services with deps → London (mocks, interaction verification)
- Value objects → Chicago (test final state)
- API integrations → London (mock external services)
- Mix both in practice (London for controllers, Chicago for domain)
Critical Success Factors:
- Tests drive design, not just verify it
- Make tests fail first to ensure they test something
- Write minimal code - no features beyond what's tested </default_to_action>
Quick Reference Card
When to Use
- Starting new feature with test-first approach
- Refactoring legacy code with test coverage
- Teaching TDD practices to team
- Choosing between mocking vs real objects
TDD Cycle
| Phase | Action | Discipline |
|---|---|---|
| Red | Write failing test | Verify it fails, check message is clear |
| Green | Minimal code to pass | No extra features, don't refactor |
| Refactor | Improve structure | Keep tests passing, no new functionality |
School Comparison
| Aspect | Chicago (Classicist) | London (Mockist) |
|---|---|---|
| Collaborators | Real objects | Mocks/stubs |
| Verification | State (assert outcomes) | Interaction (assert calls) |
| Isolation | Lower (integrated) | Higher (unit only) |
| Refactoring | Easier | Harder (mocks break) |
| Design feedback | Emerges from use | Explicit from start |
Agent Coordination
qe-test-generator: Generate tests in both schoolsqe-test-implementer: Implement minimal code (Green)qe-test-refactorer: Safe refactoring (Refactor)
What ships with it
2 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.
- 7d ago First seen · 250 lines · 37 tokens per session scan A 568c6807674a
tdd-london-chicago is a skill published in the GitHub repository summarybotng/summarybot-ng (2 stars, last pushed 3mo ago), licensed MIT. It adds 37 tokens to every session and 1,740 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 2026-09-03.
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