feat(acl): resolve the zaaktype by identificatie, not a pinned URL (S-27, closes #113) (#118)

## What & why The ACL was handed a **pinned zaaktype URL** (`Acl__Defaults__ZaaktypeUrl`) + informatieobjecttype URL. OpenZaak assigns those UUIDs at creation, so every stack had to seed the catalogus and then capture + inject the resulting URLs out of band (CI's `run-domain-check.sh`; the local `local-seed`→`acl.env` bootstrap from ADR-0020). Brittle, and a stale/placeholder URL failed opaquely (OpenZaak 400). Now **the ACL resolves them itself** from OpenZaak's Catalogi API by stable business key: - config `ZaaktypeIdentificatie` (`BIG-REGISTRATIE`) / `InformatieobjecttypeOmschrijving` (`Diploma`); - a `CachedZaaktypeCatalog` resolves **lazily on first use** and caches (success only, so a pre-publish miss is retried — no startup ordering coupling); - a clear "No published … found" error replaces the opaque placeholder 400. Design in **ADR-0021** (proposed in #117). Closes #113 Closes #117 ## Consequences (the payoff) No stack captures/injects a server-assigned URL any more — `docker-compose.yml`/`.local.yml`, `run-domain-check.sh` and `local-seed` all drop it; the local `acl.env` shrinks to a single line. **One thing S-27 can't remove** (confirmed empirically during this work): OpenZaak validates the `zaaktype` field on zaak-create with Django's URLValidator and **rejects a single-label host** (`http://openzaak:8000/…` → `zaaktype: bad-url`). So the ACL's **base URL** must still point at a URL-valid host (a container IP); that base-URL injection from ADR-0020 stays (local `acl.env` now carries only it; CI keeps `ACL_OPENZAAK_BASEURL`). ADR-0021 records this. ## Definition of Done - [x] Linked issues (#113 slice, #117 adr-proposal). - [x] TDD — resolver + gateway-lookup unit tests, updated `AclService` tests (50 unit tests green). - [x] Implementation makes them pass; refactor of both compose stacks + verify scripts follows. - [x] Conventional Commits referencing #113. - [ ] CI green — see below. - [x] `docker compose up` reaches green health — verified: fresh `make local` + `make verify-local` green with **no zaaktype-URL injection**; `acl.env` is base-URL-only. - [x] Docs — ADR-0021 + demo-script S-27 note. - [x] ADR added (ADR-0021). - [x] Demo note appended. ## Verification done locally - **50 unit tests** pass (resolver resolve/cache/retry-on-failure; gateway match/miss/blank-key; all `AclService` paths). - **6 ACL integration tests** pass against a live seeded OpenZaak — incl. resolving the zaaktype + Diploma iot by business key, and a clear error for an unknown identificatie. - **Fresh `make local` + `make verify-local`**: full flow (submit → werkbak → openbaar) green; `acl.env` = `Acl__OpenZaak__BaseUrl` only. - `make lint` clean; ACL mutation ratchet run locally (see checks). ## Notes for reviewers - `IZaakGateway` gains two resolve methods; `AclService` depends on the new `IZaaktypeCatalog` (singleton, so the cache persists). - Supersedes the pinned-URL mechanism; ADR-0021 documents that ADR-0020's `seed-env`/entrypoint shim are **simplified** (base-URL only), not deleted, because of the URLValidator constraint above. Reviewed-on: #118
2026-07-22 14:49:25 +00:00
parent 183d0bce31
commit 5de8c1e292
20 changed files with 602 additions and 100 deletions
@@ -6,6 +6,12 @@ public class AclServiceTests
 {
    private sealed class FakeGateway : IZaakGateway
    {
+        // The URLs the catalogus resolves the configured identificatie/omschrijving to (S-27).
+        public Uri ResolvedZaaktype { get; } = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+        public Uri ResolvedInformatieobjecttype { get; } = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip");
+        public string? ResolvedByIdentificatie;
+        public string? ResolvedByOmschrijving;
+
        public ZaakRequest? Captured;
        public Uri Result { get; } = new("http://openzaak/zaken/api/v1/zaken/abc");

@@ -47,6 +53,18 @@ public class AclServiceTests
            StoredDocument = request;
            return Task.FromResult(DocumentResult);
        }
+
+        public Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+        {
+            ResolvedByIdentificatie = identificatie;
+            return Task.FromResult(ResolvedZaaktype);
+        }
+
+        public Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+        {
+            ResolvedByOmschrijving = omschrijving;
+            return Task.FromResult(ResolvedInformatieobjecttype);
+        }
    }

    private static AclDefaults Defaults() => new()
@@ -54,28 +72,23 @@ public class AclServiceTests
        Bronorganisatie = "517439943",
        VerantwoordelijkeOrganisatie = "517439943",
        Vertrouwelijkheidaanduiding = "openbaar",
-        ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-        InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
+        ZaaktypeIdentificatie = "BIG-REGISTRATIE",
+        InformatieobjecttypeOmschrijving = "Diploma",
    };

+    private static AclService ServiceWith(FakeGateway gateway, AclDefaults defaults, DateOnly today) =>
+        new(gateway, defaults, new CachedZaaktypeCatalog(gateway, defaults), new FixedClock(today));
+
    private sealed class FixedClock(DateOnly today) : IClock
    {
        public DateOnly Today { get; } = today;
    }

    [Fact]
-    public async Task Opening_a_zaak_default_fills_zgw_fields_and_returns_the_zaak_url()
+    public async Task Opening_a_zaak_default_fills_zgw_fields_and_uses_the_resolved_zaaktype()
    {
        var gateway = new FakeGateway();
-        var defaults = new AclDefaults
-        {
-            Bronorganisatie = "517439943",
-            VerantwoordelijkeOrganisatie = "517439943",
-            Vertrouwelijkheidaanduiding = "openbaar",
-            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-            InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
-        };
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));

        var url = await service.OpenZaakAsync(new DomainRegistration("123456782", "reg-77"));

@@ -84,7 +97,9 @@ public class AclServiceTests
        Assert.Equal("517439943", req.Bronorganisatie);
        Assert.Equal("517439943", req.VerantwoordelijkeOrganisatie);
        Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
-        Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
+        // The zaaktype is resolved from the configured identificatie, not a pinned URL (S-27).
+        Assert.Equal("BIG-REGISTRATIE", gateway.ResolvedByIdentificatie);
+        Assert.Equal(gateway.ResolvedZaaktype, req.Zaaktype);
        Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
        // The registration reference becomes the zaak identificatie (#78).
        Assert.Equal("reg-77", req.Identificatie);
@@ -94,33 +109,24 @@ public class AclServiceTests
    public async Task Rejects_a_null_registration_without_calling_the_gateway()
    {
        var gateway = new FakeGateway();
-        var defaults = new AclDefaults
-        {
-            Bronorganisatie = "517439943",
-            VerantwoordelijkeOrganisatie = "517439943",
-            Vertrouwelijkheidaanduiding = "openbaar",
-            ZaaktypeUrl = new("http://openzaak/catalogi/api/v1/zaaktypen/big"),
-            InformatieobjecttypeUrl = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip"),
-        };
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
        Assert.Null(gateway.Captured);
    }

    [Fact]
-    public async Task Approving_a_zaak_sets_it_to_its_zaaktypes_eindstatus_dated_today()
+    public async Task Approving_a_zaak_sets_it_to_its_resolved_zaaktypes_eindstatus_dated_today()
    {
        var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");

        await service.ApproveZaakAsync(zaak);

        Assert.NotNull(gateway.Approved);
        Assert.Equal(zaak, gateway.Approved!.Value.Zaak);
-        Assert.Equal(defaults.ZaaktypeUrl, gateway.Approved.Value.Zaaktype);
+        Assert.Equal(gateway.ResolvedZaaktype, gateway.Approved.Value.Zaaktype);
        Assert.Equal(new DateOnly(2026, 6, 4), gateway.Approved.Value.Datum);
    }

@@ -128,7 +134,7 @@ public class AclServiceTests
    public async Task Approving_a_null_zaak_is_rejected_without_touching_the_gateway()
    {
        var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.ApproveZaakAsync(null!));
        Assert.Null(gateway.Approved);
@@ -138,15 +144,14 @@ public class AclServiceTests
    public async Task Cancelling_a_zaak_sets_it_to_the_cancellation_status_dated_today()
    {
        var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");

        await service.CancelZaakAsync(zaak);

        Assert.NotNull(gateway.Cancelled);
        Assert.Equal(zaak, gateway.Cancelled!.Value.Zaak);
-        Assert.Equal(defaults.ZaaktypeUrl, gateway.Cancelled.Value.Zaaktype);
+        Assert.Equal(gateway.ResolvedZaaktype, gateway.Cancelled.Value.Zaaktype);
        Assert.Equal(new DateOnly(2026, 6, 4), gateway.Cancelled.Value.Datum);
        // Cancellation must not touch the approval path.
        Assert.Null(gateway.Approved);
@@ -156,18 +161,17 @@ public class AclServiceTests
    public async Task Cancelling_a_null_zaak_is_rejected_without_touching_the_gateway()
    {
        var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.CancelZaakAsync(null!));
        Assert.Null(gateway.Cancelled);
    }

    [Fact]
-    public async Task Storing_a_diploma_default_fills_the_document_fields_and_returns_its_url()
+    public async Task Storing_a_diploma_default_fills_the_document_fields_and_uses_the_resolved_informatieobjecttype()
    {
        var gateway = new FakeGateway();
-        var defaults = Defaults();
-        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");

        var url = await service.StoreDiplomaAsync(zaak, [1, 2, 3], "diploma.pdf", "application/pdf");
@@ -175,7 +179,9 @@ public class AclServiceTests
        Assert.Equal(gateway.DocumentResult, url);
        var req = gateway.StoredDocument!;
        Assert.Equal(zaak, req.Zaak);
-        Assert.Equal(defaults.InformatieobjecttypeUrl, req.Informatieobjecttype);
+        // The informatieobjecttype is resolved from the configured omschrijving (S-27).
+        Assert.Equal("Diploma", gateway.ResolvedByOmschrijving);
+        Assert.Equal(gateway.ResolvedInformatieobjecttype, req.Informatieobjecttype);
        Assert.Equal("517439943", req.Bronorganisatie);
        Assert.Equal("openbaar", req.Vertrouwelijkheidaanduiding);
        Assert.Equal(new DateOnly(2026, 6, 4), req.Creatiedatum);
@@ -188,7 +194,7 @@ public class AclServiceTests
    [Fact]
    public async Task Storing_a_diploma_rejects_null_or_blank_arguments()
    {
-        var service = new AclService(new FakeGateway(), Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(new FakeGateway(), Defaults(), new DateOnly(2026, 6, 4));
        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.StoreDiplomaAsync(null!, [1], "d.pdf", "application/pdf"));
@@ -201,7 +207,7 @@ public class AclServiceTests
    public async Task Reading_a_zaak_reference_returns_the_zaaks_identificatie()
    {
        var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));
        var zaak = new Uri("http://openzaak/zaken/api/v1/zaken/abc");

        var reference = await service.GetZaakReferenceAsync(zaak);
@@ -214,7 +220,7 @@ public class AclServiceTests
    public async Task Reading_a_null_zaak_reference_is_rejected()
    {
        var gateway = new FakeGateway();
-        var service = new AclService(gateway, Defaults(), new FixedClock(new DateOnly(2026, 6, 4)));
+        var service = ServiceWith(gateway, Defaults(), new DateOnly(2026, 6, 4));

        await Assert.ThrowsAsync<ArgumentNullException>(() => service.GetZaakReferenceAsync(null!));
        Assert.Null(gateway.ReadReferenceFor);
@@ -675,4 +675,153 @@ public class OpenZaakGatewayTests

        await Assert.ThrowsAsync<ArgumentNullException>(() => Gateway(handler).StoreDocumentAsync(null!));
    }
+
+    // ── Catalogi resolution by business key (S-27) ────────────────────────────────────────────────
+
+    [Fact]
+    public async Task Resolves_the_published_zaaktype_url_by_identificatie()
+    {
+        HttpRequestMessage? seen = null;
+        var handler = new StubHandler(req =>
+        {
+            seen = req;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = JsonContent.Create(new
+                {
+                    results = new[] { new { url = "http://openzaak/catalogi/api/v1/zaaktypen/big", identificatie = "BIG-REGISTRATIE" } },
+                }),
+            });
+        });
+
+        var url = await Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE");
+
+        Assert.Equal("http://openzaak/catalogi/api/v1/zaaktypen/big", url.ToString());
+        Assert.Equal(HttpMethod.Get, seen!.Method);
+        // Filters to the published zaaktype with that identificatie, and authenticates.
+        Assert.Contains("/catalogi/api/v1/zaaktypen", seen.RequestUri!.ToString());
+        Assert.Contains("status=definitief", seen.RequestUri!.Query);
+        Assert.Contains("identificatie=BIG-REGISTRATIE", seen.RequestUri!.Query);
+        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_throws_a_clear_error_when_none_is_published()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { results = Array.Empty<object>() }),
+        }));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        Assert.Contains("BIG-REGISTRATIE", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolves_the_informatieobjecttype_url_by_omschrijving()
+    {
+        HttpRequestMessage? seen = null;
+        var handler = new StubHandler(req =>
+        {
+            seen = req;
+            return Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+            {
+                Content = JsonContent.Create(new
+                {
+                    results = new[]
+                    {
+                        new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/other", omschrijving = "Overig" },
+                        new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/dip", omschrijving = "Diploma" },
+                    },
+                }),
+            });
+        });
+
+        var url = await Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma");
+
+        // Queries the published informatieobjecttypen collection, and matches on omschrijving (not position).
+        Assert.Contains("/catalogi/api/v1/informatieobjecttypen", seen!.RequestUri!.ToString());
+        Assert.Contains("status=definitief", seen.RequestUri!.Query);
+        Assert.Equal("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip", url.ToString());
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_throws_when_the_response_carries_no_results()
+    {
+        // No "results" property → the page's Results is null; the gateway must treat that as "none
+        // found" (not dereference null).
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { count = 0 }),
+        }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_throws_when_the_response_carries_no_results()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new { count = 0 }),
+        }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+    }
+
+    [Fact]
+    public async Task Resolving_a_zaaktype_surfaces_a_non_success_catalogi_response()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.InternalServerError)
+        {
+            Content = new StringContent("boom"),
+        }));
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).ResolveZaaktypeUrlAsync("BIG-REGISTRATIE"));
+        // The error names the resource being queried and includes OpenZaak's body.
+        Assert.Contains("zaaktypen", ex.Message);
+        Assert.Contains("boom", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_surfaces_a_non_success_catalogi_response()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.InternalServerError)
+        {
+            Content = new StringContent("boom"),
+        }));
+
+        var ex = await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+        Assert.Contains("informatieobjecttypen", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_an_informatieobjecttype_throws_when_no_omschrijving_matches()
+    {
+        var handler = new StubHandler(_ => Task.FromResult(new HttpResponseMessage(HttpStatusCode.OK)
+        {
+            Content = JsonContent.Create(new
+            {
+                results = new[] { new { url = "http://openzaak/catalogi/api/v1/informatieobjecttypen/other", omschrijving = "Overig" } },
+            }),
+        }));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).ResolveInformatieobjecttypeUrlAsync("Diploma"));
+        Assert.Contains("Diploma", ex.Message);
+    }
+
+    [Fact]
+    public async Task Resolving_rejects_a_blank_business_key_without_calling_openzaak()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveZaaktypeUrlAsync(" "));
+        await Assert.ThrowsAnyAsync<ArgumentException>(() => Gateway(handler).ResolveInformatieobjecttypeUrlAsync(" "));
+    }
 }
@@ -0,0 +1,92 @@
+using Acl.Application;
+
+namespace Acl.Tests;
+
+public class ZaaktypeCatalogTests
+{
+    // A gateway that only supports resolution; the other members are unused here.
+    private sealed class ResolvingGateway : IZaakGateway
+    {
+        public int ZaaktypeCalls;
+        public int InformatieobjecttypeCalls;
+        public string? LastIdentificatie;
+        public string? LastOmschrijving;
+        public int ThrowZaaktypeTimes;
+        public Uri ZaaktypeUrl { get; } = new("http://openzaak/catalogi/api/v1/zaaktypen/big");
+        public Uri InformatieobjecttypeUrl { get; } = new("http://openzaak/catalogi/api/v1/informatieobjecttypen/dip");
+
+        public Task<Uri> ResolveZaaktypeUrlAsync(string identificatie, CancellationToken ct = default)
+        {
+            ZaaktypeCalls++;
+            LastIdentificatie = identificatie;
+            if (ZaaktypeCalls <= ThrowZaaktypeTimes)
+                throw new InvalidOperationException("no published zaaktype yet");
+            return Task.FromResult(ZaaktypeUrl);
+        }
+
+        public Task<Uri> ResolveInformatieobjecttypeUrlAsync(string omschrijving, CancellationToken ct = default)
+        {
+            InformatieobjecttypeCalls++;
+            LastOmschrijving = omschrijving;
+            return Task.FromResult(InformatieobjecttypeUrl);
+        }
+
+        public Task<Uri> OpenZaakAsync(ZaakRequest request, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task SetZaakToEindstatusAsync(Uri z, Uri zt, DateOnly d, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task SetZaakToCancellationStatusAsync(Uri z, Uri zt, DateOnly d, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task<string> GetZaakIdentificatieAsync(Uri z, CancellationToken ct = default) => throw new NotSupportedException();
+        public Task<Uri> StoreDocumentAsync(DocumentRequest r, CancellationToken ct = default) => throw new NotSupportedException();
+    }
+
+    private static AclDefaults Defaults() => new()
+    {
+        Bronorganisatie = "517439943",
+        VerantwoordelijkeOrganisatie = "517439943",
+        Vertrouwelijkheidaanduiding = "openbaar",
+        ZaaktypeIdentificatie = "BIG-REGISTRATIE",
+        InformatieobjecttypeOmschrijving = "Diploma",
+    };
+
+    [Fact]
+    public async Task Resolves_the_zaaktype_and_informatieobjecttype_by_their_configured_business_keys()
+    {
+        var gateway = new ResolvingGateway();
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        Assert.Equal(gateway.ZaaktypeUrl, await catalog.GetZaaktypeUrlAsync());
+        Assert.Equal(gateway.InformatieobjecttypeUrl, await catalog.GetInformatieobjecttypeUrlAsync());
+        Assert.Equal("BIG-REGISTRATIE", gateway.LastIdentificatie);
+        Assert.Equal("Diploma", gateway.LastOmschrijving);
+    }
+
+    [Fact]
+    public async Task Caches_the_resolved_urls_so_the_gateway_is_hit_once()
+    {
+        var gateway = new ResolvingGateway();
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        for (var i = 0; i < 3; i++)
+        {
+            await catalog.GetZaaktypeUrlAsync();
+            await catalog.GetInformatieobjecttypeUrlAsync();
+        }
+
+        Assert.Equal(1, gateway.ZaaktypeCalls);
+        Assert.Equal(1, gateway.InformatieobjecttypeCalls);
+    }
+
+    [Fact]
+    public async Task Does_not_cache_a_failed_resolution_so_it_is_retried()
+    {
+        // The zaaktype is not published yet on the first call; the catalog must retry (not cache the
+        // failure) so a later call succeeds once it is published.
+        var gateway = new ResolvingGateway { ThrowZaaktypeTimes = 1 };
+        var catalog = new CachedZaaktypeCatalog(gateway, Defaults());
+
+        await Assert.ThrowsAsync<InvalidOperationException>(() => catalog.GetZaaktypeUrlAsync());
+        var url = await catalog.GetZaaktypeUrlAsync();
+
+        Assert.Equal(gateway.ZaaktypeUrl, url);
+        Assert.Equal(2, gateway.ZaaktypeCalls);
+    }
+}