feat(domain): expose POST /registrations/{id}/decide for the beoordeling (refs #13)

The behandel-portal's decision reaches the domain here (via the BFF, later slices):
goedkeuren/afwijzen, idempotent, superseding the temporary /approve endpoint.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -2,19 +2,130 @@
 
 All notable changes to this project. Generated from Conventional Commits by git-cliff.
 
-## Unreleased
+## v2026.07.0 — 2026-07-14
+
+### Architecture
+- ADR-0005 adopt Stryker.NET for mutation testing (refs #47)
+- ADR-0006 — provision the ACL integration test against the compose stack (refs #46)
+- ADR-0007 + runbooks for the OZ→NRC notification wiring (refs #56)
+- ADR-0009 external-task job-worker pattern (refs #6, #60)
+- ADR-0010 BFF OIDC validation + downstream boundaries (refs #8, #63)
+
+### Bug Fixes
+- Pin OpenZaak/NRC image tags; add smoke log capture on failure (refs #30)
+- Harden oz-db healthcheck and raise compose-up timeout (refs #30)
+- Bake config into images so compose-smoke passes on CI (refs #30)
+- Nrc-init runs migrations only, not setup_configuration (refs #30)
+- Smoke waits on durable services, not the whole project (refs #30)
+- Portable health poll instead of compose --wait (refs #30)
+- Pin upload-artifact to @v3 — @v4 refuses to run on Gitea (refs #47)
+- Buffer the zaak POST body so OpenZaak accepts it (refs #46)
+- Keep dotnet format green under the shared .editorconfig (refs #65)
+- Re-export the full Utrecht package from libs/ui (refs #67)
+- Run checkAuth() at startup to end the login redirect loop (refs #67)
+- Health-check nginx over IPv4 (127.0.0.1) (refs #68)
+- Treat the http portal origin as secure so DigiD PKCE login works (refs #68)
+- Attach the DigiD token to relative BFF calls (refs #68)
+
+### Build
+- Pin Stryker.NET as a local dotnet tool (refs #47)
 
 ### CI
 - Gitea Actions pipeline + runner runbook (refs #30) (#37)
+- ACL Dockerfile + full compose stack for smoke test (refs #30)
+- Switch runner label to ubuntu-latest (refs #30)
+- Run the mutation ratchet as a parallel CI job (refs #47)
+- Publish the Stryker HTML report as a CI artifact (refs #47)
+- Run the ACL integration test as a Gitea Actions job (refs #46)
+- Keep the integration lane local-only; document the runner gap (refs #46)
+- Run the ACL integration test in CI inside the compose network (closes #55) (refs #46)
+- Run the Event Subscriber + projection-api in compose and verify end-to-end (refs #7)
+- Containerize, wire into compose, and verify end-to-end (refs #6)
+- Make Stryker report upload best-effort (refs #62)
+- Retrigger after runner cleanup (refs #6)
+- Retrigger CI (refs #6)
+- Retrigger CI after gitea restart (refs #6)
+- Compose wiring, verify-bff live check, mutation baseline (refs #8)
+- Nx frontend lane (lint/test/build) (refs #65)
+- Serve the self-service app in compose (refs #68)
+- Run Vitest ahead of the production build to stop worker-start timeout (refs #68)
+- Cache the NuGet package store across the .NET jobs (refs #73)
+- Run Playwright from the prebuilt image instead of downloading browsers (refs #73)
 
 ### Chores
 - Add idempotent Gitea backlog seeder
 - Remove bootstrap scripts from main (#35)
+- Contributor workflow — templates, git-cliff, gitea-workflow doc (closes #31) (#38)
 
 ### Documentation
 - Split S-00 into sub-slices (refs #1) (#33)
+- MkDocs scaffold + ADR-0001 + README quickstart (closes #32) (#39)
+- Tighten gitea-actions-gotchas, add local compose (refs #30)
+- ADR-0008 read projection store + demo note for the event path (refs #7)
+- Demo note for submitting a registration (S-05) (refs #6)
+- Demo note for the BFF front door (S-07) (refs #8)
+- Split S-08 into S-08a-d (refs #65)
+- Frontend-decisions + demo note for S-08a (refs #65)
+- Record the orval generator choice (refs #66)
+- Record NL DS + DigiD decisions and demo note (refs #67)
+- Serving/e2e decisions + walking-skeleton demo note (refs #68)
 
 ### Features
 - Placeholder BFF + /health endpoint (closes #28) (#34)
 - Containerize BFF + compose-up smoke (closes #29) (#36)
+- OpenZaak + Postgres + Redis up in compose (refs #10) (#40)
+- Seed BIG catalogus + JWT client for OpenZaak (refs #2) (#41)
+- Open Notificaties up + shared network (closes #2) (#42)
+- Keycloak with four mock realms (closes #3) (#43)
+- Flowable + registratie.bpmn external task (closes #4) (#44)
+- ACL skeleton — OpenZaak default-fill (refs #5) (#45)
+- Add bind-mount local compose for no-make/Windows dev (refs #30)
+- Publish the BIG zaaktype on demand via OZ_PUBLISH (refs #46)
+- Wire OpenZaak → Open Notificaties notifications (refs #56)
+- Project zaak-created notifications into the read projection (refs #7)
+- Persist the read projection and expose webhook + read APIs (refs #7)
+- Enforce the callback bearer before reading the body (refs #7)
+- Implement the Registration aggregate invariants (refs #6)
+- Implement SubmitRegistration and OpenZaakWorker (refs #6)
+- Implement the Flowable Workflow Client and ACL client (refs #6)
+- Expose POST /registrations and the read endpoint (refs #6)
+- Implement self-service submit and openbaar lookup (refs #8)
+- Committed OpenAPI contract + drift guard (refs #8)
+- Self-service portal placeholder page (refs #65)
+- Expose the generated BFF client + repeatable generate target (refs #66)
+- Implement the DigiD registration submit page (refs #67)
+- Runtime config + nginx serve/proxy image (refs #68)
+- Surface submit failures with a retryable alert (refs #68)
+- One citizen reference across self-service and the openbaar register (#79)
+
+### Other
+- Openbaar Register portal — public lookup (#76)
+- Approval flow — temp admin endpoint + status transition to projection (#77)
+
+### Refactor
+- Bake config via dockerfile_inline, drop Dockerfile files (refs #30)
+- Use upstream images verbatim, seed config via docker cp (refs #30)
+- One verify-stack stage for all live-stack checks (closes #58) (refs #46 #56)
+
+### Tests
+- BDD acceptance scenario for opening a zaak (closes #5) (#49)
+- Kill surviving mutants — assert CRS headers, guards, error paths, JWT claims (refs #47)
+- Add Stryker config + mutation make target recording the 95% baseline (refs #47)
+- Integration test opens a real zaak against OpenZaak (refs #46)
+- Verify-notifications smoke + CI job for the OZ→NRC path (refs #56)
+- Project zaak-created notifications into the read projection (refs #7)
+- Ratchet projector mutation baseline to 100% (refs #7)
+- Registration aggregate invariants (refs #6)
+- SubmitRegistration + OpenZaakWorker use cases (refs #6)
+- Workflow Client, ACL client, store and job processor (refs #6)
+- Acceptance scenario for submitting a registration (refs #6)
+- Mutation baseline 90 (achieved 97.7%) + CI/Makefile wiring (refs #6)
+- Endpoints, JWT auth and public-safe projection (refs #8)
+- Acceptance scenario for BFF access (valid/invalid tokens) (refs #8)
+- Self-service portal placeholder renders (refs #65)
+- Generated BFF client is exposed and calls the endpoints (refs #66)
+- DigiD-guarded registration submit page (refs #67)
+- Walking-skeleton Playwright happy path + verify-e2e lane (refs #68)
+- Submit surfaces BFF failures instead of swallowing them (refs #68)
+- Guard that the DigiD token attaches to relative BFF calls (refs #68)
 

services/domain/Big.Api/Program.cs

@@ -24,6 +24,7 @@ builder.Services.AddHttpClient<IAclClient, AclHttpClient>();
 
 builder.Services.AddScoped<SubmitRegistration>();
 builder.Services.AddScoped<ApproveRegistration>();
+builder.Services.AddScoped<BeoordeelRegistratie>();
 builder.Services.AddScoped<OpenZaakWorker>();
 builder.Services.AddScoped<OpenZaakJobProcessor>();
 
@@ -55,6 +56,22 @@ app.MapPost("/registrations/{id}/approve", async (string id, ApproveRegistration
     return Results.NoContent();
 });
 
+// The behandelaar's beoordeling (S-12): decide a registration goedkeuren (→ INGESCHREVEN, sets the
+// zaak's final status via the ACL) or afwijzen (→ AFGEWEZEN). Idempotent. This is the domain contract
+// the behandel-portal's decision reaches through the BFF; it supersedes the temporary /approve above,
+// which is retired once the portal lands.
+app.MapPost("/registrations/{id}/decide", async (string id, DecideRequest body, BeoordeelRegistratie beoordeel, CancellationToken ct) =>
+{
+    if (!Guid.TryParse(id, out var guid))
+        return Results.NotFound();
+
+    if (!Enum.TryParse<BeoordelingsBesluit>(body.Besluit, ignoreCase: true, out var besluit))
+        return Results.BadRequest(new { error = $"Unknown besluit '{body.Besluit}'. Expected 'goedkeuren' or 'afwijzen'." });
+
+    await beoordeel.HandleAsync(new BeoordeelRegistratieCommand(new RegistrationId(guid), besluit), ct);
+    return Results.NoContent();
+});
+
 // Read a registration. Its zaak URL appears once the worker has opened the zaak (eventually).
 app.MapGet("/registrations/{id}", async (string id, IRegistrationStore store, CancellationToken ct) =>
 {
@@ -72,6 +89,8 @@ await app.RunAsync();
 
 public sealed record SubmitRegistrationRequest(string Bsn);
 
+public sealed record DecideRequest(string Besluit);
+
 public sealed record RegistrationResponse(string RegistrationId, string Status, string? ZaakUrl);
 
 public partial class Program;

services/domain/Big.Application/BeoordeelRegistratie.cs

@@ -0,0 +1,57 @@
+using Big.Domain;
+
+namespace Big.Application;
+
+/// <summary>A behandelaar's beoordeling outcome, in domain language.</summary>
+public enum BeoordelingsBesluit
+{
+    /// <summary>Approve — enter the registration in the register.</summary>
+    Goedkeuren,
+
+    /// <summary>Reject — turn the registration down.</summary>
+    Afwijzen,
+}
+
+/// <summary>A behandelaar's decision on a registration.</summary>
+public sealed record BeoordeelRegistratieCommand(RegistrationId RegistrationId, BeoordelingsBesluit Besluit);
+
+/// <summary>
+/// The beoordeling use case (S-12): apply a behandelaar's decision to a registration.
+/// <see cref="BeoordelingsBesluit.Goedkeuren"/> sets the zaak's final status via the ACL (§8.1) and
+/// advances the aggregate to INGESCHREVEN; <see cref="BeoordelingsBesluit.Afwijzen"/> advances it to
+/// AFGEWEZEN in the domain (propagating a rejection to the zaak, so the openbaar projection reflects
+/// it, is a later sub-slice of S-12). Both decisions are idempotent — a repeated or redelivered
+/// decision that matches the current terminal state is a no-op, so the ACL is not called twice.
+/// </summary>
+public sealed class BeoordeelRegistratie(IRegistrationStore store, IAclClient acl)
+{
+    public async Task HandleAsync(BeoordeelRegistratieCommand command, CancellationToken ct = default)
+    {
+        ArgumentNullException.ThrowIfNull(command);
+
+        var registration = await store.GetAsync(command.RegistrationId, ct)
+            ?? throw new InvalidOperationException($"No registration {command.RegistrationId} to decide.");
+
+        switch (command.Besluit)
+        {
+            case BeoordelingsBesluit.Goedkeuren:
+                // A repeated approval is a no-op: don't set the zaak status a second time.
+                if (registration.Status == RegistrationStatus.Ingeschreven)
+                    return;
+                if (registration.ZaakUrl is null)
+                    throw new InvalidOperationException(
+                        $"Registration {command.RegistrationId} has no zaak yet; it cannot be approved.");
+                await acl.ApproveZaakAsync(registration.ZaakUrl, ct);
+                registration.Approve();
+                break;
+
+            case BeoordelingsBesluit.Afwijzen:
+                if (registration.Status == RegistrationStatus.Afgewezen)
+                    return;
+                registration.Reject();
+                break;
+        }
+
+        await store.SaveAsync(registration, ct);
+    }
+}

services/domain/Big.Domain/Registration.cs

@@ -66,10 +66,28 @@ public sealed class Registration
     }
 
     /// <summary>
-    /// Approve the registration — the behandelaar's decision to enter it in the register. Advances
-    /// <see cref="RegistrationStatus.Ingediend"/> → <see cref="RegistrationStatus.Ingeschreven"/>.
-    /// Requires an opened zaak (the approval sets that zaak's status via the ACL), and only a
-    /// submitted registration can be approved: re-approving is rejected as an invalid transition.
+    /// A behandelaar picks the registration up for beoordeling. Advances
+    /// <see cref="RegistrationStatus.Ingediend"/> → <see cref="RegistrationStatus.InBehandeling"/>.
+    /// Re-taking one already <see cref="RegistrationStatus.InBehandeling"/> is a no-op (the same or
+    /// another behandelaar re-opens it); a decided registration can no longer be taken into behandeling.
+    /// </summary>
+    public void TakeIntoBehandeling()
+    {
+        if (Status == RegistrationStatus.InBehandeling)
+            return;
+
+        if (Status != RegistrationStatus.Ingediend)
+            throw new InvalidOperationException(
+                $"Registration {Id} is {Status}; only an INGEDIEND registration can be taken into behandeling.");
+
+        Status = RegistrationStatus.InBehandeling;
+    }
+
+    /// <summary>
+    /// Approve the registration — the behandelaar's decision to enter it in the register. Advances a
+    /// submitted or in-behandeling registration to <see cref="RegistrationStatus.Ingeschreven"/>.
+    /// Requires an opened zaak (the approval sets that zaak's status via the ACL); a registration that
+    /// has already been decided cannot be approved again.
     /// </summary>
     public void Approve()
     {
@@ -77,10 +95,27 @@ public sealed class Registration
             throw new InvalidOperationException(
                 $"Registration {Id} has no zaak yet; it cannot be approved before its zaak is opened.");
 
-        if (Status != RegistrationStatus.Ingediend)
-            throw new InvalidOperationException(
-                $"Registration {Id} is {Status}; only an INGEDIEND registration can be approved.");
-
+        RequireOpenForDecision(nameof(Approve));
         Status = RegistrationStatus.Ingeschreven;
     }
+
+    /// <summary>
+    /// Reject the registration — the behandelaar's decision not to enter it in the register. Advances a
+    /// submitted or in-behandeling registration to <see cref="RegistrationStatus.Afgewezen"/>. Unlike
+    /// approval this needs no zaak: a registration can be rejected before or after its zaak is opened.
+    /// A registration that has already been decided cannot be rejected again.
+    /// </summary>
+    public void Reject()
+    {
+        RequireOpenForDecision(nameof(Reject));
+        Status = RegistrationStatus.Afgewezen;
+    }
+
+    // A decision is only valid while the registration is still open (INGEDIEND or IN_BEHANDELING).
+    private void RequireOpenForDecision(string decision)
+    {
+        if (Status is not (RegistrationStatus.Ingediend or RegistrationStatus.InBehandeling))
+            throw new InvalidOperationException(
+                $"Registration {Id} is {Status}; only an INGEDIEND or IN_BEHANDELING registration can be decided ({decision}).");
+    }
 }

services/domain/Big.Domain/RegistrationStatus.cs

@@ -1,13 +1,20 @@
 namespace Big.Domain;
 
-/// <summary>The lifecycle states a <see cref="Registration"/> moves through. The walking
-/// skeleton knows <see cref="Ingediend"/> and the terminal <see cref="Ingeschreven"/>; withdrawal,
-/// beoordeling and herregistratie states arrive in their own slices (Iteration 2+).</summary>
+/// <summary>The lifecycle states a <see cref="Registration"/> moves through. Submission starts in
+/// <see cref="Ingediend"/>; a behandelaar takes it <see cref="InBehandeling"/> and decides it into one
+/// of the terminal states <see cref="Ingeschreven"/> (approved) or <see cref="Afgewezen"/> (rejected).
+/// Withdrawal and herregistratie states arrive in their own slices (S-11+).</summary>
 public enum RegistrationStatus
 {
     /// <summary>Submitted by the zorgprofessional; the registratie process has been started.</summary>
     Ingediend,
 
-    /// <summary>Approved: entered in the register. Terminal in the walking skeleton (S-09b).</summary>
+    /// <summary>Picked up by a behandelaar for beoordeling (S-12).</summary>
+    InBehandeling,
+
+    /// <summary>Approved: entered in the register. Terminal.</summary>
     Ingeschreven,
+
+    /// <summary>Rejected by the behandelaar. Terminal.</summary>
+    Afgewezen,
 }

services/domain/Big.Tests/BeoordeelRegistratieTests.cs

@@ -0,0 +1,142 @@
+using Big.Application;
+using Big.Domain;
+
+namespace Big.Tests;
+
+/// <summary>
+/// The beoordeling use case (S-12): a behandelaar's decision on a registration. Goedkeuren sets the
+/// zaak's final status via the ACL (§8.1) and marks the aggregate INGESCHREVEN; Afwijzen marks it
+/// AFGEWEZEN in the domain (propagating a rejection to the zaak is a later sub-slice). Both are
+/// idempotent so a repeated or redelivered decision is a no-op.
+/// </summary>
+public class BeoordeelRegistratieTests
+{
+    private static Registration WithZaak(string bsn = "123456782")
+    {
+        var registration = Registration.Submit(bsn);
+        registration.AttachZaak(FakeAclClient.DefaultZaakUrl);
+        return registration;
+    }
+
+    [Fact]
+    public async Task Goedkeuren_sets_the_zaak_status_via_the_acl_and_marks_the_registration_ingeschreven()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Goedkeuren));
+
+        var saved = await store.GetAsync(registration.Id);
+        Assert.Equal(RegistrationStatus.Ingeschreven, saved!.Status);
+        Assert.Equal(FakeAclClient.DefaultZaakUrl, acl.ApprovedZaakUrl);
+        Assert.Equal(1, acl.ApproveCallCount);
+        Assert.Equal(1, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Afwijzen_marks_the_registration_afgewezen_without_calling_the_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Afwijzen));
+
+        var saved = await store.GetAsync(registration.Id);
+        Assert.Equal(RegistrationStatus.Afgewezen, saved!.Status);
+        Assert.Equal(0, acl.ApproveCallCount);
+        Assert.Equal(1, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Goedkeuren_an_in_behandeling_registration_marks_it_ingeschreven()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        registration.TakeIntoBehandeling();
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Goedkeuren));
+
+        Assert.Equal(RegistrationStatus.Ingeschreven, (await store.GetAsync(registration.Id))!.Status);
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_command_without_touching_the_store_or_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => handler.HandleAsync(null!));
+        Assert.Equal(0, acl.ApproveCallCount);
+        Assert.Equal(0, store.SaveCount);
+    }
+
+    [Fact]
+    public async Task Deciding_an_unknown_registration_throws_and_does_not_call_the_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            handler.HandleAsync(new BeoordeelRegistratieCommand(RegistrationId.New(), BeoordelingsBesluit.Goedkeuren)));
+        Assert.Contains("No registration", ex.Message);
+        Assert.Equal(0, acl.ApproveCallCount);
+    }
+
+    [Fact]
+    public async Task Goedkeuren_before_the_zaak_is_opened_throws_without_calling_the_acl()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = Registration.Submit("123456782"); // no zaak yet
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() =>
+            handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Goedkeuren)));
+        Assert.Contains("no zaak", ex.Message);
+        Assert.Equal(0, acl.ApproveCallCount);
+    }
+
+    [Fact]
+    public async Task Re_goedkeuren_an_already_ingeschreven_registration_is_idempotent()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Goedkeuren));
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Goedkeuren));
+
+        Assert.Equal(1, acl.ApproveCallCount);
+        Assert.Equal(RegistrationStatus.Ingeschreven, (await store.GetAsync(registration.Id))!.Status);
+    }
+
+    [Fact]
+    public async Task Re_afwijzen_an_already_afgewezen_registration_is_idempotent()
+    {
+        var store = new FakeRegistrationStore();
+        var acl = new FakeAclClient();
+        var registration = WithZaak();
+        store.Seed(registration);
+        var handler = new BeoordeelRegistratie(store, acl);
+
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Afwijzen));
+        await handler.HandleAsync(new BeoordeelRegistratieCommand(registration.Id, BeoordelingsBesluit.Afwijzen));
+
+        Assert.Equal(1, store.SaveCount);
+        Assert.Equal(RegistrationStatus.Afgewezen, (await store.GetAsync(registration.Id))!.Status);
+    }
+}

services/domain/Big.Tests/RegistrationTests.cs

@@ -121,4 +121,100 @@ public class RegistrationTests
         Assert.Contains("only an INGEDIEND", ex.Message);
         Assert.Equal(RegistrationStatus.Ingeschreven, registration.Status);
     }
+
+    [Fact]
+    public void Taking_a_registration_into_behandeling_moves_it_to_in_behandeling()
+    {
+        var registration = Registration.Submit("123456782");
+
+        registration.TakeIntoBehandeling();
+
+        Assert.Equal(RegistrationStatus.InBehandeling, registration.Status);
+    }
+
+    [Fact]
+    public void Re_taking_an_in_behandeling_registration_is_idempotent()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.TakeIntoBehandeling();
+
+        registration.TakeIntoBehandeling();
+
+        Assert.Equal(RegistrationStatus.InBehandeling, registration.Status);
+    }
+
+    [Fact]
+    public void Taking_a_decided_registration_into_behandeling_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+        registration.Approve();
+
+        var ex = Assert.Throws<InvalidOperationException>(() => registration.TakeIntoBehandeling());
+        Assert.Contains("only an INGEDIEND", ex.Message);
+        Assert.Equal(RegistrationStatus.Ingeschreven, registration.Status);
+    }
+
+    [Fact]
+    public void Approving_an_in_behandeling_registration_with_a_zaak_sets_it_ingeschreven()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+        registration.TakeIntoBehandeling();
+
+        registration.Approve();
+
+        Assert.Equal(RegistrationStatus.Ingeschreven, registration.Status);
+    }
+
+    [Fact]
+    public void Rejecting_a_registration_sets_it_afgewezen()
+    {
+        var registration = Registration.Submit("123456782");
+
+        registration.Reject();
+
+        Assert.Equal(RegistrationStatus.Afgewezen, registration.Status);
+    }
+
+    [Fact]
+    public void Rejecting_needs_no_zaak()
+    {
+        // A registration can be turned down before its zaak is ever opened, so Reject must not require one.
+        var registration = Registration.Submit("123456782");
+
+        registration.Reject();
+
+        Assert.Equal(RegistrationStatus.Afgewezen, registration.Status);
+        Assert.Null(registration.ZaakUrl);
+    }
+
+    [Fact]
+    public void Rejecting_an_in_behandeling_registration_sets_it_afgewezen()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.TakeIntoBehandeling();
+
+        registration.Reject();
+
+        Assert.Equal(RegistrationStatus.Afgewezen, registration.Status);
+    }
+
+    [Fact]
+    public void Deciding_an_already_decided_registration_is_rejected()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.Reject();
+
+        var approveEx = Assert.Throws<InvalidOperationException>(() =>
+        {
+            registration.AttachZaak(new Uri("http://openzaak/zaken/api/v1/zaken/abc"));
+            registration.Approve();
+        });
+        Assert.Contains("IN_BEHANDELING", approveEx.Message);
+
+        var rejectEx = Assert.Throws<InvalidOperationException>(() => registration.Reject());
+        Assert.Contains("Afgewezen", rejectEx.Message);
+        Assert.Equal(RegistrationStatus.Afgewezen, registration.Status);
+    }
 }

tests/acceptance/Features/EenRegistratieBeoordelen.feature

@@ -0,0 +1,24 @@
+# language: en
+# Drives S-12 (#13). A behandelaar picks up a submitted registration for beoordeling and decides it:
+# goedkeuren enters it in the register (INGESCHREVEN, the zaak's final status set via the ACL, §8.1),
+# afwijzen turns it down (AFGEWEZEN). This scenario exercises the use cases against in-memory
+# stand-ins for the ACL and the store; real Flowable user-task claim/complete arrives in a later
+# sub-slice and is verified live.
+Feature: Een registratie beoordelen
+  Als behandelaar wil ik een ingediende registratie beoordelen
+  zodat deze wordt ingeschreven of afgewezen.
+
+  Scenario: Goedkeuren schrijft de registratie in via de ACL
+    Given a submitted registration with an opened zaak
+    When the behandelaar takes it into behandeling
+    Then the registration has status "INBEHANDELING"
+    When the behandelaar decides "goedkeuren"
+    Then the registration has status "INGESCHREVEN"
+    And the zaak's final status is set via the ACL
+
+  Scenario: Afwijzen wijst de registratie af zonder de ACL
+    Given a submitted registration with an opened zaak
+    When the behandelaar takes it into behandeling
+    And the behandelaar decides "afwijzen"
+    Then the registration has status "AFGEWEZEN"
+    And the ACL is not asked to set the zaak status

tests/acceptance/Steps/EenRegistratieBeoordelenSteps.cs

@@ -0,0 +1,58 @@
+using Acceptance.Support;
+using Big.Application;
+using Big.Domain;
+using Reqnroll;
+using Xunit;
+
+namespace Acceptance.Steps;
+
+/// <summary>Bindings for <c>EenRegistratieBeoordelen.feature</c> (S-12). Drives the TakeIntoBehandeling
+/// transition and the BeoordeelRegistratie use case against in-memory ports; one instance per scenario.
+/// Scoped to this feature so its "the registration has status" step does not clash with the identically
+/// phrased (but differently-asserting) step in <see cref="RegistratieIndienenSteps"/>.</summary>
+[Binding]
+[Scope(Feature = "Een registratie beoordelen")]
+public sealed class EenRegistratieBeoordelenSteps
+{
+    private readonly InMemoryAclClient _acl = new();
+    private readonly InMemoryRegistrationStore _store = new();
+    private RegistrationId _id;
+
+    [Given("a submitted registration with an opened zaak")]
+    public async Task GivenASubmittedRegistrationWithAnOpenedZaak()
+    {
+        var registration = Registration.Submit("123456782");
+        registration.AttachZaak(InMemoryAclClient.OpenedZaakUrl);
+        await _store.SaveAsync(registration);
+        _id = registration.Id;
+    }
+
+    [When("the behandelaar takes it into behandeling")]
+    public async Task WhenTheBehandelaarTakesItIntoBehandeling()
+    {
+        var registration = await _store.GetAsync(_id);
+        registration!.TakeIntoBehandeling();
+        await _store.SaveAsync(registration);
+    }
+
+    [When("the behandelaar decides \"(.*)\"")]
+    public async Task WhenTheBehandelaarDecides(string besluit)
+        => await new BeoordeelRegistratie(_store, _acl).HandleAsync(
+            new BeoordeelRegistratieCommand(_id, Enum.Parse<BeoordelingsBesluit>(besluit, ignoreCase: true)));
+
+    [Then("the registration has status \"(.*)\"")]
+    public async Task ThenTheRegistrationHasStatus(string expected)
+    {
+        var registration = await _store.GetAsync(_id);
+        Assert.NotNull(registration);
+        Assert.Equal(expected, registration.Status.ToString().ToUpperInvariant());
+    }
+
+    [Then("the zaak's final status is set via the ACL")]
+    public void ThenTheZaakFinalStatusIsSetViaTheAcl()
+        => Assert.Equal(InMemoryAclClient.OpenedZaakUrl, _acl.ApprovedZaakUrl);
+
+    [Then("the ACL is not asked to set the zaak status")]
+    public void ThenTheAclIsNotAskedToSetTheZaakStatus()
+        => Assert.Null(_acl.ApprovedZaakUrl);
+}