API Automation Demo (TypeScript + Swagger Petstore)

A demo of API automation

What this demonstrates

• API methods: GET, POST, and DELETE (cleanup)
• Request complexity: path params and nested JSON request bodies
• Response complexity: nested objects + arrays
• Advanced verification:
  • Typed schema validation using zod (deserialization-style checks)
  • Full-response snapshot verification (approval testing style)
• Builder pattern for reusable and maintainable test data setup
• Negative-path checks for invalid payloads and missing resources
• Mocking strategy using nock for deterministic API tests

Tech stack

• TypeScript
• Vitest
• Axios
• Zod
• Nock

The architecture jigsaw

This is a conceptual view of how everything hangs together

flowchart LR
    A["Vitest (test runner)"] --> B["Test Files<br/>mock + live"]
    B --> C["PetstoreClient"]
    C --> D["Axios (HTTP client)"]
    C --> E["Zod (request/response validation)"]

    subgraph Mocked Path
      B --> M["Nock intercepts HTTP"]
      M --> D
      D --> N["No real network call"]
    end

    subgraph Live Path
      D --> P["Swagger Petstore API"]
    end

    E --> Q["Typed, validated data<br/>for assertions"]
    A --> R["Assertions + snapshots + reports"]
    Q --> R

Loading

• Vitest runs the suite and performs assertions/snapshot checks.
• PetstoreClient is the thin abstraction your tests call.
• Axios performs HTTP requests.
• Zod validates request and response payloads at runtime while keeping TypeScript types aligned.
• Nock is used only for mock tests to intercept HTTP and avoid external dependencies.

Project structure

src/
  client/
    petstoreClient.ts
  config/
    env.ts
  models/
    pet.ts
tests/
  builders/
    petBuilder.ts
  live/
    petstore.live.test.ts
    setup.ts
  mock/
    petstore.mock.test.ts
    setup.ts
.github/workflows/
  ci.yml

Quick start

1. Install dependencies

npm install

2. Run deterministic mocked tests (recommended default)

npm run test:mock

3. Run live Petstore tests

npm run test:live

Environment

Copy .env.example to .env if you want to override the default API base URL.

PETSTORE_BASE_URL=https://petstore.swagger.io/v2

Notes

• npm run test:mock runs only mock tests to keep CI stable and fast.
• Live tests are intentionally separate because public API data/state can be unstable.