How do I install the API Mocking skill?

Run npx skillmds@latest add christopherlouet/api-mocking in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

Is API Mocking safe to use?

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Which AI agents work with API Mocking?

This skill is tagged as working with Claude Code, Claude.ai, OpenAI Codex. SKILL.md is an open format, so most agents that read a skills directory can load it too.

Is API Mocking free to use?

Yes. Installing skills from SkillMD is free, and the skill stays under its author's original license.

Who published API Mocking?

christopherlouet (@christopherlouet) published this skill. Their other Agent Skills are listed on their SkillMD profile.

API Mocking by christopherlouet — Agent Skill

Name: API Mocking
Author: christopherlouet

File contents

API Mocking (pointer)

MSW handler API, browser/node setup, install commands and request-interception internals are canonical at vendor docs and drift on each release:

MSW — mswjs.io (recommended default; browser worker + Node server, single handler set)
nock — github.com/nock/nock (Node-only HTTP interception)
json-server — github.com/typicode/json-server (full REST fake server from a JSON file)
Mirage JS — miragejs.com (browser-only, models + factories)

Tool selection (version-agnostic)

Need to mock HTTP for tests/dev?
├── Browser AND Node from one handler set → MSW
├── Node-only unit tests, low ceremony → nock
├── Need a stateful REST fake server (CRUD) → json-server
└── Browser-only with relational fixtures (factories) → Mirage JS

Foundation discipline (keep across releases)

Type-safe mocks: derive mock payloads from the same TypeScript types as the real API (e.g. shared types/api.ts). A mock that compiles against stale types is the #1 source of mock-prod divergence.
Reset between tests: always resetHandlers() (MSW) or cleanAll() (nock) in afterEach — leaked state across tests is a debugging tax.
Realistic failure modes: simulate 5xx/timeouts/auth errors, not just happy paths. The mock is only useful if it exercises the same edge cases as prod.
Unhandled = error: in tests use onUnhandledRequest: 'error' (MSW) so a typo'd URL fails loudly instead of silently passing.

---name: api-mockingdescription: API mock configuration for tests. Trigger when the user wants to mock APIs, use MSW, or test without a backend.---# API Mocking (pointer)MSW handler API, browser/node setup, install commands and request-interception internals are canonical at vendor docs and drift on each release:- **MSW** — [mswjs.io](https://mswjs.io) (recommended default; browser worker + Node server, single handler set)- **nock** — [github.com/nock/nock](https://github.com/nock/nock) (Node-only HTTP interception)- **json-server** — [github.com/typicode/json-server](https://github.com/typicode/json-server) (full REST fake server from a JSON file)- **Mirage JS** — [miragejs.com](https://miragejs.com) (browser-only, models + factories)## Tool selection (version-agnostic)```Need to mock HTTP for tests/dev?├── Browser AND Node from one handler set → MSW├── Node-only unit tests, low ceremony → nock├── Need a stateful REST fake server (CRUD) → json-server└── Browser-only with relational fixtures (factories) → Mirage JS```## Foundation discipline (keep across releases)- **Type-safe mocks**: derive mock payloads from the same TypeScript types as the real API (e.g. shared `types/api.ts`). A mock that compiles against stale types is the #1 source of mock-prod divergence.- **Reset between tests**: always `resetHandlers()` (MSW) or `cleanAll()` (nock) in `afterEach` — leaked state across tests is a debugging tax.- **Realistic failure modes**: simulate 5xx/timeouts/auth errors, not just happy paths. The mock is only useful if it exercises the same edge cases as prod.- **Unhandled = error**: in tests use `onUnhandledRequest: 'error'` (MSW) so a typo'd URL fails loudly instead of silently passing.## See also- `dev-tdd` — mocks live in test setup; this skill activates from TDD work- `qa-e2e` — Playwright/Cypress tests often layer MSW for deterministic stubs- `dev-tdd` (test-infrastructure setup) — wires the global `setupServer` into vitest/jest config

Frequently asked questions

API Mocking