testing

A set of testing rules for TypeScript projects that use Vitest, a JavaScript and TypeScript test framework. It defines where tests go, how they are named, how they run, and what cases they should cover.

In plain words
What is it for?
Use it when adding unit or integration tests, checking success and error paths, testing file operations with temporary folders, mocking services, and validating inputs.
Why use it?
It gives coding agents consistent expectations for writing tests instead of leaving test structure and coverage decisions unclear. It also discourages tests that call real external services.

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/pranav-karra-3301/tuck/testing
Clone the repo
git clone --depth 1 https://github.com/Pranav-Karra-3301/tuck

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 428 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found 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 $0.00000 $0.00428
Opus 5 $0.00000 $0.00214
Sonnet 5 $0.00000 $0.00086
Haiku 4.5 $0.00000 $0.00043

Measured 2d ago against content hash 72e14dd8d294, method: parsed. Prices are Anthropic first-party input rates as of 2026-08-30, from the pricing page.

Security

Grade A, and why

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 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.

.cursor/rules/testing.mdc · 87 lines

What it actually says

Testing Rules

Test Framework

  • Use Vitest for all tests
  • Tests mirror src/ structure in tests/
  • Test files end with .test.ts

Running Tests

pnpm test              # Run all tests
pnpm test:watch        # Watch mode
pnpm test:coverage     # With coverage

Test Structure

import { describe, it, expect, beforeEach, afterEach } from 'vitest';

describe('functionName', () => {
  beforeEach(() => {
    // Setup before each test
  });

  afterEach(() => {
    // Cleanup after each test
  });

  it('should do X when given Y', () => {
    const result = functionName(input);
    expect(result).toBe(expected);
  });

  it('should throw CustomError when given invalid input', () => {
    expect(() => functionName(invalid)).toThrow(CustomError);
  });
});

Test Guidelines

  1. Test both paths - Success AND error cases
  2. Use temp directories - For file operations
  3. Mock external services - Don't hit real APIs
  4. Meaningful assertions - Test behavior, not implementation
  5. Descriptive names - "should X when Y" format

What to Test

Unit Tests

  • Individual functions
  • Edge cases
  • Error handling
  • Input validation

Integration Tests

  • Command workflows
  • Git operations
  • File system changes

Coverage

  • Aim for high coverage but prioritize meaningful tests
  • Don't test implementation details
  • Focus on public API behavior

Test File Location

src/lib/paths.ts      -> tests/lib/paths.test.ts
src/commands/add.ts   -> tests/commands/add.test.ts

NEVER

  • Skip tests in PRs
  • Commit failing tests
  • Test private implementation details
  • Leave flaky tests unfixed
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. 2d ago First seen · 87 lines · 0 tokens per session scan A 72e14dd8d294

Subscribe to this mod's changes

testing is a cursor rule published in the GitHub repository Pranav-Karra-3301/tuck (14 stars, last pushed 1mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 428 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 2026-08-30.