Pact vs Prism: Which Contract Mocking Tool Fits?
Quick answer: Pact and Prism are both used around contracts and mocks, but they start from opposite ends. Pact is consumer-driven: the consumer records the interactions it expects, and those are replayed against the provider in its pipeline to prove the two still agree. Prism is spec-driven: it reads an OpenAPI document and serves mock responses or validates traffic against that spec. Choose Pact…
Pact and Prism are contract mocking tools, but they serve different purposes. Pact is consumer-driven, meaning it focuses on the interactions expected by a consumer. It creates a contract based on what the consumer actually calls in a mock provider, and then verifies that the provider still meets those expectations before deployment. Prism, on the other hand, is spec-driven. It takes an existing OpenAPI document and uses it to generate mock responses or validate live traffic against the specification.
Choosing between the two depends on where your "contract" lives. If your source of truth is the consumer's interactions, Pact is the better fit. If the OpenAPI document is your reference, Prism offers a lighter solution. Both tools can coexist - a team could use Prism for local development and consumer-driven contracts in CI for services that truly need integration guarantees. However, neither tool can replace real end-to-end testing or guarantee correctness outside the scope of what they cover.
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