Prism vs Testcontainers

Free and open source

Free tier available

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

Free. Testcontainers Cloud, which offloads container execution, is a paid Docker product.

Everything, self-hosted

The libraries are free and open source.

Established

Stoplight (SmartBear) · since 2017

Category standard

AtomicJar (Docker) · since 2015

• The mock is generated from the spec, so it cannot silently diverge from the contract.
• Validation proxy mode checks that a real implementation matches its own spec.
• Zero configuration beyond having an OpenAPI file.

• Tests run against the real database engine, so dialect and behaviour differences surface early.
• Containers are disposable, which removes shared-state flakiness entirely.
• Excellent language coverage with idiomatic APIs.

• Useless without an accurate OpenAPI document.
• Limited stateful behaviour — it is spec-driven, not scenario-driven.
• Generated example data is uninteresting unless examples are in the spec.

• Requires a Docker daemon in CI, which not every environment provides.
• Container startup adds seconds to each test run unless reused carefully.
• Heavier resource usage than in-memory alternatives.

Design-first API teams who want mocks that are provably in sync with the contract.

Integration tests that currently use in-memory databases and lie to you.