testing

A set of rules for writing and organizing software tests, which check that code behaves as expected.

In plain words
What is it for?
Use it when creating or reviewing tests, including tests for errors, boundaries, external services, and unusual input.
Why use it?
It provides consistent expectations for coverage, test structure, test data, mocks, flaky tests, and edge cases.

Cursor rule

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/dasomel/oh-my-cursor/testing
Clone the repo
git clone --depth 1 https://github.com/dasomel/oh-my-cursor
Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 372 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 $0.00372
Opus 5 $0.00000 $0.00186
Sonnet 5 $0.00000 $0.00074
Haiku 4.5 $0.00000 $0.00037

Measured yesterday against content hash 7ec2929c8485, 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 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.

rules/practices/testing.mdc · 56 lines

What it actually says

Testing Standards

Coverage Targets

  • Line coverage: ≥ 80%
  • Branch coverage: ≥ 75% on critical paths
  • Function coverage: ≥ 90%

Test Structure (AAA Pattern)

it('should return error when input is empty', () => {
  // Arrange
  const input = ''

  // Act
  const result = validateInput(input)

  // Assert
  expect(result.ok).toBe(false)
  expect(result.error).toBe('Input cannot be empty')
})

Naming

  • Describe behavior, not implementation: 'should return 404 when user not found'
  • Not: 'test getUserById with invalid id'

Test Data

  • Use factories/builders, not hardcoded values
  • Seed random data with faker for variety
  • Reset state between tests

Mocking Rules

  • Mock external dependencies (HTTP, DB, filesystem)
  • Don't mock your own code (that's testing the mock)
  • Verify mock calls when behavior matters, not just return values

Flaky Test Prevention

  • No setTimeout or sleep in tests
  • Use waitFor with explicit conditions
  • Deterministic test order (each test is independent)
  • No shared mutable state between tests

Edge Cases Checklist

  • Empty/null input
  • Maximum/minimum boundary values
  • Unicode and special characters
  • Concurrent operations
  • Network timeout/error
  • Permission denied
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 · 56 lines · 0 tokens per session scan A 7ec2929c8485

Subscribe to this mod's changes

testing is a cursor rule published in the GitHub repository dasomel/oh-my-cursor (2 stars, last pushed 5mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 372 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.