30-testing

A set of software-testing rules built around a test-first loop: write a failing test, make it pass, then improve the code. It also requires checking linting, types, and tests.

In plain words
What is it for?
Use it when adding or changing behavior, especially when you need to describe which checks ran and which could not be run.
Why use it?
It reduces the chance of changing behavior without noticing and makes verification part of each code change.

Cursor rule for Cursor

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 rules/luxvil/ai-coding-rules/30-testing
Clone the repo
git clone --depth 1 https://github.com/Luxvil/ai-coding-rules

Made for: Cursor.

Per session 101 This file is loaded in full into every session.
When invoked 101 The same file — it is already loaded in full.
Security scan A 0 findings. Scan, not verified.
Origin 100% copy Near-identical to another mod 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 $0.00101 $0.00101
Opus 5 $0.00051 $0.00051
Sonnet 5 $0.00020 $0.00020
Haiku 4.5 $0.00010 $0.00010

Measured yesterday against content hash d6fc36c9f217, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

30-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.

Origin

This is a copy

100% identical to 30-testing — 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.

.cursor/rules/30-testing.mdc · 21 lines

What it actually says

Testing Rules

Test-First Loop

  1. Write failing test
  2. Implement until green
  3. Refactor (tests stay green)

Verification

  • Run lint → typecheck → tests
  • State what’s not run and why

Guard Clauses

  • Prefer early returns to reduce nesting and complexity
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. yesterday First seen · 21 lines · 101 tokens per session scan A d6fc36c9f217

Subscribe to this mod's changes

30-testing is a cursor rule published in the GitHub repository Luxvil/ai-coding-rules (3 stars, last pushed 2d ago), licensed MIT. It adds 101 tokens to every session, about $0.0005 per session on Opus 5. A static security scan graded it A with 0 findings. It is 100% identical to 30-testing, differing in 0 lines, and is treated as a copy.