Snaplet Seed vs Mock Service Worker

Free and open source

Free and open source

The Seed library is open source and free; note that Snaplet wound down its hosted product, so treat this as a library rather than a service.

Free and open source. You pay in engineering time and CI minutes.

Everything, self-hosted

Everything, self-hosted

Emerging

Snaplet · since 2021

Category standard

OSS community · since 2020

• Schema-aware generation means the data actually inserts and the app actually works.
• Deterministic seeds make failing tests reproducible.
• Good TypeScript ergonomics with Prisma and Drizzle.

• One set of handlers reused across unit, component, E2E and local development.
• Application code is completely unaware it is being mocked — no test-only branches.
• Supports REST and GraphQL with the same model.

• The company wound down its hosted business — evaluate the library's maintenance status before depending on it.
• PostgreSQL-centric.
• TypeScript ecosystem only.

• JavaScript ecosystem only.
• Service Worker registration adds a setup step and occasional caching confusion.
• Handlers can drift from the real API without contract verification.

TypeScript teams that want each developer and CI run to start from a clean, coherent database.

Front-end teams that want one mocking approach across every kind of test.