Testing Multiple Runtimes¶

Two runtimes means two test runtimes. Each context is tested independently — Catalog tests don't need Lending to exist, and vice versa.

Per-Context Isolation¶

[TestRuntime<CatalogRuntime>]
public partial class TestCatalogRuntime;

[TestRuntime<LendingRuntime>]
public partial class TestLendingRuntime;

Each generates its own Create() and CreateConfigured(). Each wires its own stores and event queues. They don't interfere with each other.

Two Ways to Test¶

Unit Tests with Spies¶

[Test]
public async Task BorrowBook_PublishesDomainEvent()
{
    var runtime = TestLendingRuntime.Create();
    runtime.PatronStore.Seed(new Patron { Id = patronId, Name = "Alice", Email = "alice@example.com" });

    await LendingDispatch.BorrowBook(patronId, bookId).RunAsync(runtime);

    runtime.LendingDomainEvents.AssertContains<DomainEvent.BookBorrowed>();
}

Create() gives you: - .Seed() — pre-populate stores without going through commands - .SaveCalls — verify what was saved - .AssertContains<T>() — verify events were enqueued

Behavior Tests¶

[Test]
public async Task BorrowBook_CreatesLoan()
{
    var runtime = TestLendingRuntime.CreateConfigured();

    var fin = await (
        from _ in LendingStore.Patrons.Save<LendingRuntime>(patron)
        from loanId in LendingDispatch.BorrowBook(patronId, BookId.New())
        from loans in LendingDispatch.GetPatronLoans(patronId)
        select loans
    ).RunAsync(runtime);

    await Assert.That(fin).IsSuccMatching(r => r.Data.Count == 1);
}

CreateConfigured() returns the production runtime. Seed data via dispatch. Verify outcomes via queries. This test works identically against InMemory stores and real Postgres — flip with one environment variable:

dotnet test                       # InMemory stores
INTEGRATION=true dotnet test      # real Postgres (via OnConfigureIntegration hook)

Naming Convention¶

Both types live in the same test file. The method name tells you which path it uses:

• _PublishesDomainEvent, _RecordsSaveCall → Create() (spy/contract tests)
• _CreatesLoan, _SetsDueDate, _Fails_WhenNotFound → CreateConfigured() (behavior tests)

Integration Testing with Real Infrastructure¶

Implement OnConfigureIntegration to swap in real stores:

[TestRuntime<LendingRuntime>]
public partial class TestLendingRuntime
{
    partial void OnConfigureIntegration() =>
        IntegrationDefaults.Configure(this);
}

IntegrationDefaults is a static helper that starts Testcontainers, runs migrations, and provides real store implementations from DI. See Integration Testing for the full pattern.

Cross-Context Integration Tests¶

To test the full event flow (Lending publishes → Catalog subscribes), compose both runtimes in a single test host. This is an advanced pattern covered in the integration testing docs — the key idea is that both runtimes share the same in-process event channel, so events flow between them synchronously.