REST Assured vs Specmatic

Free and open source

Free tier available

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

Open source core; commercial support and an enterprise insights product are sold separately.

Everything, self-hosted

Open-source core covering contract testing and stubbing.

Widely used

OSS community · since 2010

Emerging

Specmatic · since 2020

• API tests live in the codebase, versioned and reviewed with the service.
• Readable given/when/then chains that map directly onto HTTP semantics.
• Full access to Java for setup, data and assertions.

• Spec-driven rather than consumer-driven, so it needs far less cross-team process than Pact.
• The same spec produces both the provider test and the consumer mock.
• Covers async messaging (Kafka, AsyncAPI) as well as HTTP.

• Java only, and requires developers rather than manual testers.
• No GUI, so exploratory request work needs a separate client.
• Verbose for very large payload assertions.

• Only works if your specs are accurate and maintained.
• Smaller community than Pact, with fewer worked examples.
• Primarily JVM-oriented tooling.

JVM teams that want API tests in the same repository as the service.

Spec-first organisations that want contract enforcement without the Pact process overhead.