testing

A set of testing rules built around TDD, or test-driven development: write a failing test, make it pass with minimal code, then improve the code. It also defines test structure, coverage targets, and rules for independent tests.

In plain words
What is it for?
Use it when creating or changing test files, including writing regression tests for bug fixes, organizing Arrange-Act-Assert tests, and checking coverage for business logic, utilities, APIs, and UI components.
Why use it?
It gives development work a repeatable way to prove behavior and helps prevent bugs from returning. It also discourages tests that depend on implementation details or shared mutable data.

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/jy315189/everything-cursor/testing
Clone the repo
git clone --depth 1 https://github.com/jy315189/everything-cursor

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.
When invoked 416 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 $0.00416
Opus 5 $0.00000 $0.00208
Sonnet 5 $0.00000 $0.00083
Haiku 4.5 $0.00000 $0.00042

Measured yesterday against content hash 7b2692536d22, 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.

.cursor/rules/testing.mdc · 55 lines

What it actually says

Testing Rules

TDD Protocol

RED → GREEN → REFACTOR — no exceptions
  1. Define interfaces/types FIRST (the contract)
  2. Write failing tests (must fail for the right reason)
  3. Implement MINIMAL code to pass
  4. Verify all tests GREEN
  5. Refactor while keeping tests green
  6. Check coverage ≥ 80%

Test Structure: Arrange-Act-Assert

describe('[Module]', () => {
  describe('[method]', () => {
    it('[expected behavior in plain English]', async () => {
      // Arrange — set up test data and mocks
      // Act — call the function under test (ONE call)
      // Assert — verify the outcome
    })
  })
})

Coverage Targets

Area Target Rationale
Business logic (services) 100% Core value, must be correct
Utilities / helpers ≥ 90% Widely reused, high leverage
API handlers ≥ 80% Integration tests cover happy + error paths
UI components ≥ 70% Focus on interactions, not visual layout
Overall ≥ 80% Baseline confidence

Mandatory Rules

  • Every bug fix MUST include a regression test
  • Tests MUST be independent (no shared mutable state)
  • Test BEHAVIOR, not implementation details
  • Mock external dependencies, use real logic for your code
  • No any in test files — test types matter too
  • No test.skip or describe.skip in committed code
  • Flaky tests are bugs — fix or delete, never ignore
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 · 55 lines · 0 tokens per session scan A 7b2692536d22

Subscribe to this mod's changes

testing is a cursor rule published in the GitHub repository jy315189/everything-cursor (2 stars, last pushed 6mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 416 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.