Jeremy D. Miller • 8/3/2026

Declarative Testing Helper for Marten or Polecat Projections

This article introduces EventProjectionScenario, a declarative testing API for Marten and Polecat projections. It allows developers to script sequences of event appends and document assertions, then execute them end-to-end. The scenario supports all projection lifecycles, including asynchronous ones, by automatically managing a projection daemon. Key features include batched commits, automatic stream ID generation, and assertion steps that run after projected data is up to date. The author seeks feedback and hints at future integration with 'Spec Driven Development' in the Critter Stack.

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#Event Sourcing #Declarative Testing #Critter Stack