Parallel development
How to Build a Frontend Before the Backend Is Ready
Build the frontend before the backend is ready by agreeing on contracts, serving realistic local data, and testing every important UI state. Keep assumptions explicit so the later integration is a controlled change rather than a surprise.
By Mock API Studio · Published September 17, 2026 · Updated September 17, 2026
Agree on contracts before implementations
Write down resource paths, methods, TypeScript response shapes, authentication, query conventions, and known errors. Mark unsettled decisions and assign an owner; a mock should expose uncertainty, not hide it.
Create realistic and repeatable data
Use semantic field names, enums for finite states, a fixed seed, and enough records for scrolling and pagination. Include values that affect layout: long labels, absent optionals, zero totals, and old dates.
Model nested resources deliberately
Configure parent-child keys when screens navigate from customers to orders or projects to tasks. Generated foreign keys stay valid and deleting a referenced parent returns 409 rather than silently orphaning children.
GET /customers/:customerId/orders
POST /customers/:customerId/ordersTest loading, empty, success, and error states
Add fixed latency for loading UI, reset to an empty dataset, use stable records for success, and enable 503 injection for generic failures. Exercise auth failures and missing-record 404s separately.
Loading: 1200 ms fixed latency
Empty: 0 generated records
Success: seed 42, 25 records
Failure: 100% error rate for a focused checkPrevent integration surprises
Share examples with backend developers, review field casing and nullability, and avoid adding behavior the planned API cannot support. Test generated OpenAPI output as a communication aid, not proof of the final implementation.
Move to the real API
Swap the environment base URL, run contract and integration suites, compare pagination and error envelopes, verify auth, and remove mock-specific assumptions. Keep the mock for local development and rare-state reproduction if it remains useful.
Related questions
What should be agreed first?
Start with paths, methods, response shapes, auth expectations, query conventions, and the errors the UI must handle.
Keep exploring
Last updated September 17, 2026. Product behavior described here is verified against the current Mock API Studio runtime.