From REST to Events: API Workflow Testing and Mocking with a Single Arazzo Spec

APIs rarely work in isolation. Real-world usage involves multiple steps across both synchronous REST calls and asynchronous events, where the outcome of each step determines the journey a particular interaction takes. While testing individual endpoints is necessary, it’s not sufficient. It is equally important to validate how those endpoints and events work together as part of a real workflow.

Enter the Arazzo Specification, which describes complete workflows including inputs, outputs, step dependencies, and success/failure criteria—across OpenAPI (REST) and AsyncAPI (events). In this talk, we’ll demonstrate how you can leverage Arazzo to drive end-to-end API workflow testing and mocking in a completely no-code manner.

We’ll show how Arazzo + Specmatic enables shift-left testing of entire API journeys, spanning both sync and async operations. You’ll see how mocking complete workflows can unblock frontend teams, simulate event-driven flows, and accelerate CI pipelines. The session will also walk through the full lifecycle—how we design a multi-step journey, author or generate an Arazzo spec to capture it, and ensure both providers and consumers adhere to the same contract—thereby enabling independent, parallel development and deployment of services and components in complex, event-driven microservice architectures.