A set of testing rules for React applications using React Testing Library, Jest, and tools for simulating user actions. It focuses on checking what users can see and do.

Use it to test forms, buttons, text, and other user interactions by querying roles, labels, and visible content, with test IDs used only when needed.

It avoids tests that depend on internal implementation details, which can break during harmless code changes. Accessible queries also encourage interfaces that work with assistive technology.

testing — Cursor rule by Farzannajipour

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/farzannajipour/cursor-react-rules/testing

Clone the repo

git clone --depth 1 https://github.com/Farzannajipour/cursor-react-rules

Made for: Cursor.

Per session 0 Nothing until a file matches its globs; then the whole rule loads.

When invoked 617 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.

Model	Per session	Once invoked
Fable 5	$0.00000	$0.00617
Opus 5	$0.00000	$0.00309
Sonnet 5	$0.00000	$0.00123
Haiku 4.5	$0.00000	$0.00062

Measured yesterday against content hash a736d3533370, 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 · 116 lines

How it starts

The opening of the file, as written. The whole thing — 116 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Testing Standards

Testing Library

Use React Testing Library
Use @testing-library/user-event for interactions
Use Jest as test runner

Testing Principles

Test User Behavior, Not Implementation

// ❌ Bad - testing implementation
expect(component.state.count).toBe(1);

// ✅ Good - testing user-visible behavior
expect(screen.getByText(/count: 1/i)).toBeInTheDocument();

Use Accessible Queries

Priority order:

getByRole - Accessibility-first
getByLabelText - Forms
getByText - User-visible text
getByTestId - Last resort

Example Test Pattern:

import { render, screen, waitFor } from '@testing-library/react';
import userEvent from '@testing-library/user-event';

describe('LoginForm', () => {
  it('submits form with valid credentials', async () => {
    const user = userEvent.setup();
    const mockSubmit = jest.fn();
    
    render(<LoginForm onSubmit={mockSubmit} />);
    
    await user.type(screen.getByLabelText(/email/i), '[email protected]');
    await user.type(screen.getByLabelText(/password/i), 'password123');
    await user.click(screen.getByRole('button', { name: /log in/i }));
    
    await waitFor(() => {
      expect(mockSubmit).toHaveBeenCalledWith({
        email: '[email protected]',
        password: 'password123',
      });
    });
  });
});

What to Test

Components:

Rendering with different props
User interactions (click, type, etc.)
Loading and error states
Accessibility

Hooks:

Initial state
All actions/methods
Edge cases
Cleanup

Integration:

Complete user flows
API interactions (mocked)
State updates
Navigation

Mocking

Mock External Dependencies:

jest.mock('next/navigation', () => ({
  useRouter: jest.fn(),
}));

jest.mock('@/lib/api', () => ({
  fetchUser: jest.fn(),
}));

Mock API Calls:

global.fetch = jest.fn(() =>
  Promise.resolve({
    ok: true,
    json: async () => ({ data: 'test' }),
  })
) as jest.Mock;

Read the full file on GitHub · 116 lines

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.

yesterday First seen · 116 lines · 0 tokens per session scan A a736d3533370

Subscribe to this mod's changes

testing is a cursor rule published in the GitHub repository Farzannajipour/cursor-react-rules (2 stars, last pushed 7mo ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 617 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.

Frontend Testing Writing and docs

testing