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.
npx skills add quatico-solutions/agent-skills --skill jest-testing-conventionsgit clone --depth 1 https://github.com/quatico-solutions/agent-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/quatico-solutions/agent-skills/jest-testing-conventions)<a href="https://agentmods.dev/skills/quatico-solutions/agent-skills/jest-testing-conventions"><img src="https://agentmods.dev/badge/skills/quatico-solutions/agent-skills/jest-testing-conventions/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/quatico-solutions/agent-skills/jest-testing-conventions"><img src="https://agentmods.dev/badge/skills/quatico-solutions/agent-skills/jest-testing-conventions.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 5.1 | $0.00076 | $0.02917 |
| Opus 5 | $0.00038 | $0.01458 |
| Sonnet 5 | $0.00015 | $0.00583 |
| Haiku 4.5 | $0.00008 | $0.00292 |
Grade A, and why
jest-testing-conventions 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 10d 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.
How it starts
The opening of the file, as written. The whole thing — 486 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Jest Testing Conventions
TDD Flow
Red-Green-Refactor, including the stopping rule and verification budget, lives in the test-driven-development skill. This skill covers the Jest mechanics only.
Overview
Master three functions: jest.fn(), jest.spyOn(), jest.mock().
Core principle: Mocks are necessary evil. Prefer real code. Use mocks only when unavoidable.
Naming Conventions
Variable Naming
| Name | Purpose | Example |
|---|---|---|
testObj |
Object under test | const testObj = new OrderService() |
target |
Function under test | const target = jest.fn() |
target* |
Specific mock target | targetAdd, targetFetch |
mock* |
Mock implementation | mockUserService, mockResponse |
actual |
Result from code | const actual = testObj.calculate() |
expected |
Expected value | const expected = 42 |
Test Structure
describe("OrderService", () => {
describe("calculateTotal", () => {
it("returns sum of item prices", () => {
// Arrange
const testObj = new OrderService();
const mockItems = [{ price: 10 }, { price: 20 }];
const expected = 30;
// Act
const actual = testObj.calculateTotal(mockItems);
// Assert
expect(actual).toBe(expected);
});
});
});
The Three Core Functions
jest.fn() - Stub a Function
Creates a mock function that can be observed and configured.
// Basic stub
const target = jest.fn();
target("foo");
expect(target).toHaveBeenCalledWith("foo");
// With return value
const target = jest.fn().mockReturnValue("bar");
expect(target()).toBe("bar");
// With implementation
const target = jest.fn((x) => x * 2);
expect(target(5)).toBe(10);
// With promise resolution
const target = jest.fn().mockResolvedValue({ data: "result" });
await expect(target()).resolves.toEqual({ data: "result" });
// One-time implementation
const target = jest.fn()
.mockReturnValueOnce("first")
.mockReturnValueOnce("second")
.mockReturnValue("default");
What ships with it
3 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- 10d ago First seen · 486 lines · 76 tokens per session scan A 90125c388084
jest-testing-conventions is a skill published in the GitHub repository quatico-solutions/agent-skills (2 stars, last pushed 6d ago), licensed MIT. It adds 76 tokens to every session and 2,917 once invoked, about $0.0004 per session on Opus 5. 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.
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