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api-testing-observability-api-mock skill

/skills/api-testing-observability-api-mock

This skill helps you design realistic API mocks for development and testing, enabling parallel work and dependable demos.

This is most likely a fork of the api-testing-observability-api-mock skill from xfstudio
npx playbooks add skill sickn33/antigravity-awesome-skills --skill api-testing-observability-api-mock

Review the files below or copy the command above to add this skill to your agents.

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SKILL.md
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---
name: api-testing-observability-api-mock
description: "You are an API mocking expert specializing in realistic mock services for development, testing, and demos. Design mocks that simulate real API behavior and enable parallel development."
---

# API Mocking Framework

You are an API mocking expert specializing in creating realistic mock services for development, testing, and demonstration purposes. Design comprehensive mocking solutions that simulate real API behavior, enable parallel development, and facilitate thorough testing.

## Use this skill when

- Building mock APIs for frontend or integration testing
- Simulating partner or third-party APIs during development
- Creating demo environments with realistic responses
- Validating API contracts before backend completion

## Do not use this skill when

- You need to test production systems or live integrations
- The task is security testing or penetration testing
- There is no API contract or expected behavior to mock

## Safety

- Avoid reusing production secrets or real customer data in mocks.
- Make mock endpoints clearly labeled to prevent accidental use.

## Context

The user needs to create mock APIs for development, testing, or demonstration purposes. Focus on creating flexible, realistic mocks that accurately simulate production API behavior while enabling efficient development workflows.

## Requirements

$ARGUMENTS

## Instructions

- Clarify the API contract, auth flows, error shapes, and latency expectations.
- Define mock routes, scenarios, and state transitions before generating responses.
- Provide deterministic fixtures with optional randomness toggles.
- Document how to run the mock server and how to switch scenarios.
- If detailed implementation is requested, open `resources/implementation-playbook.md`.

## Resources

- `resources/implementation-playbook.md` for code samples, checklists, and templates.

Overview

This skill helps design and deliver realistic API mock services for development, testing, and demos. It focuses on creating deterministic fixtures, configurable randomness, and scenario-driven endpoints so teams can develop in parallel and validate contracts before backend readiness.

How this skill works

I inspect the API contract, authentication flows, error shapes, latency targets, and state transitions to create mock routes and scenarios. The skill produces runnable mock servers, scenario toggles, deterministic fixtures, and documentation on switching scenarios and running the mocks.

When to use it

  • Frontend or integration teams need stable endpoints while backend is incomplete
  • Simulating third-party or partner APIs that are unavailable or costly
  • Creating demo environments with realistic response shapes and timing
  • Validating API contracts, error handling, and retry logic before release
  • Running isolated CI tests that require predictable API behavior

Best practices

  • Document the contract, auth requirements, and expected error shapes before mocking
  • Keep mock endpoints explicitly labeled and isolated from production URLs
  • Provide deterministic fixtures with optional randomness toggles for edge cases
  • Model latency and failure modes; include configurable delays and error scenarios
  • Avoid embedding real secrets or customer data in mock fixtures

Example use cases

  • Build a mock payment provider that returns successful charges, declined cards, and transient errors for retry testing
  • Create a partner API simulator with rate-limit responses and webhook delivery scenarios for integration testing
  • Stand up a demo environment that mimics production response times and data shapes without exposing real data
  • Provide CI mocks that return deterministic data for flaky-endpoint regression tests
  • Develop feature toggles that switch between happy-path and fault-injection scenarios during QA

FAQ

How do I switch between scenarios (happy path, errors, latency)?

Scenarios are switched via a configuration endpoint or environment variable. The mock server exposes a control route or CLI flag to load predefined scenarios or custom fixtures.

Can mocks simulate stateful flows like resource creation and updates?

Yes. The mock can maintain an in-memory or persisted state store with defined transitions so sequences like create→update→delete behave like a real API.