Nagare.Testing 0.15.2

Nagare 流れ

Event sourcing for .NET — flow in, truth out.

Events are the natural language of change. Something happened. Then something else. The stream moves forward, never backward, and the truth is always the whole story.

Nagare is an event sourcing framework for .NET that gets out of your way. Define what your domain means, and let the framework carry the rest.

public class BookAggregate : Aggregate<BookCommand, BookEvent, BookState>
{
 private readonly EventHandlers<BookEvent, BookState> _events =
 new EventHandlersBuilder<BookEvent, BookState>()
 .On<BookAdded>((state, e) =>
 state with { Exists = true, Title = e.Title })
 .On<BookBorrowed>((state, e) =>
 state with { IsBorrowed = true, BorrowerId = e.BorrowerId })
 .Build();

 private readonly CommandHandlers<BookCommand, BookEvent, BookState> _commands =
 new CommandHandlersBuilder<BookCommand, BookEvent, BookState>()
 .On<AddBook>((state, cmd) =>
 state.Exists
 ? Then.Reject("Book already exists")
 : Then.Persist(new BookAdded(cmd.Title, cmd.Author, cmd.Isbn)))
 .On<BorrowBook>((state, cmd) =>
 !state.Exists ? Then.Reject("Book does not exist")
 : state.IsBorrowed ? Then.Reject("Book is already borrowed")
 : Then.Persist(new BookBorrowed(cmd.BorrowerId, DateTimeOffset.UtcNow)))
 .Build();

 protected override EventHandlers<BookEvent, BookState> RegisterEventHandlers() => _events;

 protected override CommandHandlers<BookCommand, BookEvent, BookState> RegisterCommandHandlers() => _commands;
}

Commands say what you want. Events say what happened. State is what's true right now. That's it.

Test like you think

harness
 .Given(new BookAdded("Dune", "Herbert", "978-0441172719"))
 .When(new BorrowBook("user-42"))
 .ThenAccepted()
 .ThenExpect<BookBorrowed>(e => e.BorrowerId == "user-42");

harness
 .Given(new BookAdded(...), new BookBorrowed(...))
 .When(new BorrowBook("user-99"))
 .ThenRejected("already borrowed");

No database. No DI container. Just the domain, speaking for itself.

Packages

Claude Code plugin

Nagare ships a Claude Code plugin with skills for aggregate design, event naming, projections, testing, and store adapters.

# Add the marketplace
/plugin marketplace add ceracare/nagare

# Install the plugin
/plugin install nagare@ceracare-nagare

# Reload to activate
/reload-plugins

Get started

builder.Services.AddNagare();
builder.Services.AddAggregate<BookAggregate, BookCommand, BookEvent, BookState>();

See for a complete example, or read the full documentation.

Operational dashboard

Nagare.Dashboard is an embedded operational UI — a single NuGet package mounted as ASP.NET Core middleware. Live event tail, time-machine timeline per stream, provenance lens for individual events, process inspector, projections + checkpoints, outbox + dead-letter triage with gated replay. Hangfire-style mounting; dark-first Linear/Stripe-school aesthetic; prose-explained events via the optional IEventExplainer<TEvent> contract.

builder.Services.AddNagareDashboard();
builder.Services.UseLocalDevAuthorization(); // dev only — production needs an INagareDashboardAuthorizationFilter
app.MapNagareDashboard(); // mounts at /_nagare

Fail-closed by default — the dashboard returns 403 to every request unless the host registers an authorization filter. Three presets ship: NagareLocalDevFilter, NagareReadOnlyFilter, and a declarative NagareCapabilityFilter for claim/role gating.

See the dashboard guide and event explainers.

Nagare (流れ) — the flow of water, the passage of time, the course of events.