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 Cratis/AI --skill tddgit clone --depth 1 https://github.com/Cratis/AIWrote 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/cratis/ai/tdd)<a href="https://agentmods.dev/skills/cratis/ai/tdd"><img src="https://agentmods.dev/badge/skills/cratis/ai/tdd/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/cratis/ai/tdd"><img src="https://agentmods.dev/badge/skills/cratis/ai/tdd.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 | $0.00096 | $0.01358 |
| Opus 5.5 | $0.00038 | $0.00543 |
| Sonnet 5.5 | $0.00019 | $0.00272 |
| Haiku 4.5 | $0.00010 | $0.00136 |
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 1mo 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.
This is a copy
100% identical to tdd — 0 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 124 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Community Test-Driven Development Best Practices
Comprehensive guide to Test-Driven Development practices, designed for AI agents and LLMs. Contains 42 rules across 8 categories, prioritized by impact to guide test writing, refactoring, and code generation.
When to Apply
Reference these guidelines when:
- Writing new tests using TDD workflow
- Implementing the red-green-refactor cycle
- Designing test structure and organization
- Creating test data and fixtures
- Reviewing or refactoring existing test suites
TDD Workflow
- RED: Write a failing test that defines desired behavior
- GREEN: Write minimal code to make the test pass
- REFACTOR: Clean up code while keeping tests green
- Repeat for each new behavior
Rule Categories by Priority
| Priority | Category | Impact | Prefix |
|---|---|---|---|
| 1 | Red-Green-Refactor Cycle | CRITICAL | cycle- |
| 2 | Test Design Principles | CRITICAL | design- |
| 3 | Test Isolation & Dependencies | HIGH | isolate- |
| 4 | Test Data Management | HIGH | data- |
| 5 | Assertions & Verification | MEDIUM | assert- |
| 6 | Test Organization & Structure | MEDIUM | org- |
| 7 | Test Performance & Reliability | MEDIUM | perf- |
| 8 | Test Pyramid & Strategy | LOW | strat- |
Quick Reference
1. Red-Green-Refactor Cycle (CRITICAL)
cycle-write-test-first- Write the Test Before the Implementationcycle-minimal-code-to-pass- Write Only Enough Code to Pass the Testcycle-refactor-after-green- Refactor Immediately After Greencycle-verify-test-fails-first- Verify the Test Fails Before Writing Codecycle-small-increments- Take Small Incremental Stepscycle-maintain-test-list- Maintain a Test List
2. Test Design Principles (CRITICAL)
design-test-behavior-not-implementation- Test Behavior Not Implementationdesign-one-assertion-per-test- One Logical Assertion Per Testdesign-descriptive-test-names- Use Descriptive Test Namesdesign-aaa-pattern- Follow the Arrange-Act-Assert Patterndesign-test-edge-cases- Test Edge Cases and Boundariesdesign-avoid-logic-in-tests- Avoid Logic in Tests
What ships with it
47 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.
- AGENTS.md 8.4 KB
- assets/templates/_template.md 774 B
- metadata.json 1.1 KB
- README.md 4.2 KB
- references/_sections.md 1.9 KB
- references/assert-custom-matchers.md 2.3 KB
- references/assert-error-messages.md 1.8 KB
- references/assert-no-assertions-antipattern.md 2.2 KB
- references/assert-snapshot-testing.md 2.1 KB
- references/assert-specific-assertions.md 1.9 KB
- references/cycle-maintain-test-list.md 2.0 KB
- references/cycle-minimal-code-to-pass.md 1.8 KB
- references/cycle-refactor-after-green.md 1.8 KB
- references/cycle-small-increments.md 2.1 KB
- references/cycle-verify-test-fails-first.md 1.8 KB
- references/cycle-write-test-first.md 2.0 KB
- references/data-avoid-mystery-guests.md 2.0 KB
- references/data-builder-pattern.md 2.6 KB
- references/data-minimal-setup.md 1.8 KB
- references/data-unique-identifiers.md 2.3 KB
- references/data-use-factories.md 2.3 KB
- references/design-aaa-pattern.md 2.0 KB
- references/design-avoid-logic-in-tests.md 2.3 KB
- references/design-descriptive-test-names.md 1.7 KB
- references/design-one-assertion-per-test.md 2.2 KB
- references/design-test-behavior-not-implementation.md 2.0 KB
- references/design-test-edge-cases.md 2.4 KB
- references/isolate-deterministic-tests.md 2.1 KB
- references/isolate-mock-external-dependencies.md 1.8 KB
- references/isolate-no-shared-state.md 1.8 KB
- references/isolate-prefer-stubs-over-mocks.md 2.4 KB
- references/isolate-use-dependency-injection.md 2.5 KB
- references/org-file-structure.md 1.6 KB
- references/org-group-by-behavior.md 2.1 KB
- references/org-parameterized-tests.md 2.4 KB
- references/org-setup-teardown.md 2.3 KB
- references/org-test-utilities.md 2.3 KB
- references/perf-avoid-network-calls.md 2.0 KB
- references/perf-avoid-sleep.md 2.2 KB
- references/perf-fast-unit-tests.md 1.7 KB
- references/perf-fix-flaky-tests.md 2.2 KB
- references/perf-parallelize-tests.md 2.3 KB
- references/strat-coverage-targets.md 2.2 KB
- references/strat-e2e-critical-paths.md 2.5 KB
- references/strat-integration-boundaries.md 2.4 KB
- references/strat-mutation-testing.md 2.1 KB
- references/strat-test-pyramid.md 2.3 KB
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.
- 1mo ago First seen · 124 lines · 96 tokens per session scan A f1bd0e195037
tdd is a skill published in the GitHub repository Cratis/AI (4 stars, last pushed yesterday), licensed MIT. It adds 96 tokens to every session and 1,358 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it A with 0 findings. It is 100% identical to tdd, differing in 0 lines, and is treated as a copy.
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