Test placeholder data

Test & Placeholder Data APIs

Wire a demo against live fake data in one call. The mistake this prevents: hand-writing a 40-line mock array (or standing up a local json-server) when a keyless hosted API already serves richer, more realistic data - and the demo then never exercises real fetch/loading/error paths.

Ranked APIs

1. DummyJSON (dummyjson.com) - DEFAULT. 190+ products, users, carts, posts, recipes with realistic fields; search, pagination, field selection; fake write endpoints for full CRUD demos. No key.
2. JSONPlaceholder (jsonplaceholder.typicode.com) - the classic minimal set (posts/comments/todos/users) when the tutorial audience expects it or you need the flattest possible shape. No key.
3. RandomUser (randomuser.me) - generated people with names, emails, avatars, addresses. Use for user-directory and profile-card UIs. No key.
4. Lorem Picsum (picsum.photos) - placeholder photos at any size. No key.

Procedure

1. Match the API to the demo's domain: e-commerce/dashboard → DummyJSON products or carts; social/feed → DummyJSON posts or JSONPlaceholder; people/profiles → RandomUser; image slots → Picsum.
2. Make pagination and search real - DummyJSON supports it server-side, so demo the actual pattern instead of slicing a local array (templates below).
3. Seed deterministically when it matters. RandomUser output changes per call; pin it with &seed=demo so screenshots and tests reproduce. Picsum: use /id/{n}/ URLs, not /random.
4. Label fake writes. DummyJSON's POST/PUT/DELETE return plausible responses but persist nothing - say so in the demo README/comments so nobody files a bug that "saves don't stick".

Ask the user only if missing: domain of data (default: products), row count (default: 10), whether writes are needed (default: read-only).

URL templates + real response shapes

DummyJSON - read, search, paginate, select:

https://dummyjson.com/products/1
https://dummyjson.com/products?limit=10&skip=20&select=title,price,rating
https://dummyjson.com/products/search?q=phone
https://dummyjson.com/users        https://dummyjson.com/carts        https://dummyjson.com/posts

{"id":1,"title":"Essence Mascara Lash Princess","category":"beauty","price":9.99,
 "rating":2.56,"stock":99,"brand":"Essence","thumbnail":"...","images":["..."],
 "dimensions":{"width":15.14,"height":13.08},"reviews":[{"rating":2,"comment":"..."}]}

List endpoints wrap results: {"products":[...],"total":194,"skip":20,"limit":10} - read total for pager math. Fake CRUD: POST /products/add, PUT /products/1, DELETE /products/1 (echo back, no persistence).

JSONPlaceholder - flat classic resources:

https://jsonplaceholder.typicode.com/posts/1
https://jsonplaceholder.typicode.com/posts?userId=1
https://jsonplaceholder.typicode.com/posts/1/comments

{"userId":1,"id":1,"title":"sunt aut facere...","body":"quia et suscipit..."}

100 posts, 200 todos, 10 users; text is Latin filler. Writes are fake here too.

RandomUser - generated people:

https://randomuser.me/api/?results=25&nat=us,gb&seed=demo

{"results":[{"name":{"first":"Regina","last":"Fisher"},"email":"[email protected]",
  "location":{"city":"York","state":"Massachusetts","country":"United States"},
  "picture":{"large":"https://randomuser.me/api/portraits/women/88.jpg"},
  "login":{"uuid":"c305bcf6-..."}}],"info":{"seed":"demo","results":25}}

Top level is always results[] even for one user. Trim payload with &inc=name,email,picture.

Lorem Picsum - images:

https://picsum.photos/id/237/400/300          ← deterministic (dog photo, 400×300)
https://picsum.photos/seed/{any-string}/400/300   ← deterministic by seed
https://picsum.photos/v2/list?page=1&limit=30     ← JSON metadata: id, author, download_url

Image URLs 302-redirect to the file - fine in <img src>, but follow redirects when fetching programmatically. ?grayscale&blur=2 for effects.

Deliverable

Working fetch code (or curl) against the chosen endpoint with real pagination/search wired, deterministic seeds where repeatability matters, and an explicit note on any fake-write endpoints.

Do NOT use - reach for X instead

• Local fixtures, factories, or builders inside a test suite - test-data-builder. This skill is for hosted fake data behind real HTTP.
• Mocking a network call in unit tests - mock-stub-designer; don't point unit tests at live placeholder APIs (network flake becomes test flake).
• Real stock photography with search, licensing, and attribution (Unsplash, Pexels, Pixabay) - stock-photo-api; Picsum here is throwaway layout filler only.
• Real data needs - weather-climate, geo-places, finance-fx, or the public-data-api-picker router. Demo data in a real feature is a bug.
• Load testing - these are free community services; don't benchmark against them.

Quality bar

• The demo exercises at least one real HTTP concern (loading state, pagination, or error path) that a hardcoded array could not.
• Repeatable output wherever the UI is screenshotted or asserted on (seeds pinned).
• Any fake-persistence endpoint is labeled as such where the next developer will see it.

Sourced and liveness-verified from the public-apis project (MIT).