cratis-chronicle-read-model-specifications

Chronicle read-model specifications

ReadModelScenario<TReadModel> runs a projection or a reducer in-process against a sequence of events. No Chronicle server, no database, no network — the events go in, the materialized instance comes out.

Pure reducer decisions use Specification plus a direct method call by default, with the event and current state supplied explicitly (for a self model, Model.Reduce(@event, current)). Add ReadModelScenario<TReadModel> only where declarative projection behavior, event dispatch, filtering, metadata or read-model wiring contribute proof.

For a read-model scenario specification the Given is the act. There is no separate When: seeding the events is what makes the projection run.

Product sources

Package	Purpose
Cratis.Chronicle.Testing	Source/Clients/Testing/ReadModels/ReadModelScenario.cs: scenario selection, self and nominated reducers
Cratis.Chronicle	Source/Clients/DotNET/Reducers/{SelfReducerMethods,RegisteredReducerReadModel}.cs, ReadModels/ReadModelBuilderOwnership.cs: supported forms and ownership
Cratis.Specifications.XUnit	The Specification base and the ShouldXxx assertions

Source: Source/Clients/Testing/ReadModels/ in Cratis/Chronicle.

dotnet add package Cratis.Chronicle.Testing

Reverify against the Chronicle repository before claiming support for another version.

Route near misses

• Event appending, constraints, or the event log's own behavior: use cratis-chronicle-event-specifications.
• A command running through validators, Provide() and Handle(): use cratis-application-slice-specifications.
• Deciding what the read model or projection should be: use cratis-chronicle-read-model, cratis-chronicle-projection, or cratis-chronicle-reducer.
• The scope is model-first (its read-model specification blocks and then readmodel rows are the contract). Decide this with the decision rule in cratis-screenplay-modeling-lifecycle: model-first only when an accepted model under the model root covers this scope, or the repository is opted in (opted in per general.md "Model first"; where cratis-screenplay-modeling-lifecycle is installed, run its scripts/model-first-status.mjs); framework, infrastructure, client, adapter and not-opted-in brownfield work stays code-first. Opted in but no model for this scope: model it first (cratis-screenplay-discovery, then cratis-screenplay-slice-design) before writing specifications. If those Screenplay skills are not installed, say so and stop; never author .play from memory. Never edit Stage-managed output, and never change a model specification to match existing code. Author model specifications with cratis-screenplay-specifications and cratis-screenplay-scenario-coverage; check finished code against them with cratis-application-slice-conformance.