MagicCSharp.Testing

MagicCSharp.Testing

Test doubles for the framework's own seams, so a test of a use case is new PlaceOrderUseCase(...) and an assertion. No test framework dependency, no database, no containers — add MagicCSharp.Testing.Database when you need those.

The fakes for your interfaces — FakeOrdersRepository, a recording IEventDispatcher — are yours to write, a few lines each against the interface the use case asked for. What ships here is the doubles for the seams the framework owns:

Type	Replaces	Why
FakeTimeProvider	TimeProvider	.NET's own test clock, brought in by this package. Move time by hand; a thirty-day late fee is testable in milliseconds.
FakeKeyGen	IKeyGenService	Snowflake ids derived from the test's TimeProvider, so ids and timestamps agree.
SyncEventDispatcher	IEventDispatcher	Runs handlers inline and records them, so you can assert without sleeping.
InMemoryDistributedLockProvider	IDistributedLockProvider	Real mutual exclusion in-process, re-entrant during inline event dispatch.
TrackingDistributedLockProvider	IDistributedLockProvider	Grants everything, records the names — for asserting what was locked.

dotnet add package MagicCSharp.Testing

A use case, directly

var timeProvider = new FakeTimeProvider(new DateTimeOffset(2026, 3, 1, 0, 0, 0, TimeSpan.Zero));

var applyLateFees = new ApplyLateFeesUseCase(new FakeLeasesRepository(), timeProvider);

timeProvider.Advance(TimeSpan.FromDays(31));
await applyLateFees.Execute();

FakeTimeProvider comes from Microsoft's Microsoft.Extensions.TimeProvider.Testing, which this package references. SetUtcNow and Advance move it — forward only; it refuses to go back. Because it is .NET's own abstraction it also fakes what waits on time: Task.Delay(delay, timeProvider), PeriodicTimer and timed CancellationTokenSources complete when the test moves the clock, so a background service's loop can be tested without waiting for it.

Wiring a host

For a test that boots the application — WebApplicationFactory, or a ServiceCollection of your own — replace the framework's registrations:

var timeProvider = new FakeTimeProvider(new DateTimeOffset(2026, 3, 1, 0, 0, 0, TimeSpan.Zero));

services.RemoveAll<TimeProvider>();
services.AddSingleton<TimeProvider>(timeProvider);

services.RemoveAll<IKeyGenService>();
services.AddSingleton<IKeyGenService>(new FakeKeyGen(timeProvider));

services.RemoveAll<IDistributedLockProvider>();
services.AddSingleton<IDistributedLockProvider, InMemoryDistributedLockProvider>();

services.RemoveAll<IEventDispatcher>();
services.AddSingleton<IEventDispatcher>(sp =>
    new SyncEventDispatcher(sp.GetRequiredService<IAsyncEventDispatcher>()));

Asserting on events

await createOrder.Execute(new CreateOrderRequest { UserId = 1, ProductIds = [2, 3] });

Assert.True(eventDispatcher.HasDispatchedEvent<OrderCreatedEvent>());
Assert.Single(eventDispatcher.GetDispatchedEvents<OrderCreatedEvent>());
Assert.True(eventDispatcher.HasDispatchedEvent<OrderCreatedEvent>(orderCreatedEvent => orderCreatedEvent.UserId == 1));

DispatchedEvents is everything in order; ClearDispatchedEvents() resets between phases of one test.

One deliberate difference from production

SyncEventDispatcher runs handlers inline, inside whatever lock the emitting use case holds. In production dispatch is fire-and-forget, so handlers run after that lock is released. InMemoryDistributedLockProvider closes the gap: while SyncEventDispatcher is dispatching, a handler re-acquiring a name the emitter holds gets a no-op handle rather than deadlocking. The window is scoped to that one dispatch, so genuinely concurrent flows still get ordinary mutual exclusion.

Related packages

• MagicCSharp.Testing.Database — repository tests against a real PostgreSQL in a container
• MagicCSharp — the seams these replace

The whole picture, and the optional repository layout: github.com/MagicDoorInc/MagicCSharp. MIT.