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 rules/peerigon/configs/coding-styleguide-testinggit clone --depth 1 https://github.com/peerigon/configsWhat 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 | $0.00000 | $0.00546 |
| Opus 5 | $0.00000 | $0.00273 |
| Sonnet 5 | $0.00000 | $0.00109 |
| Haiku 4.5 | $0.00000 | $0.00055 |
Grade A, and why
coding-styleguide-testing 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 yesterday.
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 — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Testing
General principle
Important: Aim for the smallest high-value test set that protects behavior, interface contracts, invariants, and regression-prone paths. Focus on testing behavior rather than implementation details.
Structure & Organization
- Order of tests: Match the order of tests to the order of symbols in the source file
- One describe per export: Provide a describe block for each exported symbol (function, class, constant)
- Hierarchical grouping: Use nested describe() blocks - outer for function/class, inner for scenarios
- Logical categorization: Group by behavior, input type, or state (e.g., "with valid input", "error handling")
- Each it() should test a single behavior
- Put setup hooks and test cases first; keep local helper functions and fixtures at the bottom of the file
Test Coverage
- Happy path: Test expected behavior with typical inputs
- Edge cases: Test boundaries, empty values, maximum/minimum values
- Error scenarios: Test all failure modes with proper error type/message validation
- Type variations: Test all relevant data types (primitives, objects, arrays, functions)
- Falsy values: Explicitly test null, undefined, 0, "", false, NaN
Type Safety
- Type annotations: Include explicit types in test variables to verify inference
- Compile-time checks: Some tests exist just to verify type compatibility
- Type tests for generics: Add type tests for generic functions, classes, etc. Use the test runner's type testing tool when available (e.g. with Vitest:
expectTypeOf)
Best Practices
- Descriptive names: Use clear it() descriptions stating expected behavior
- Avoid "should" phrasing in it(): Use verbs like "does" or "returns" to describe behavior
- Isolation: Each test should be independent and not rely on others
- Arrange-Act-Assert: Follow AAA pattern for test structure
- DRY with helpers: Extract repetitive setup into helper functions
- Use real-life examples and descriptive names for test data
Assertions
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.
- yesterday First seen · 51 lines · 546 tokens per session scan A 20628db55fa7
coding-styleguide-testing is a cursor rule published in the GitHub repository peerigon/configs (4 stars, last pushed 20d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 546 tokens. 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 2026-08-31.
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