test(acl): kill surviving mutants — assert CRS headers, guards, error paths, JWT claims (refs #47)

Stryker exposed thin ACL tests (35% mutation score): the suite never asserted
the geo CRS headers, the ArgumentNullException guards, the non-success and
empty-body error paths, or the structure of the minted ZGW JWT — so mutating
any of those survived.

Strengthen the unit tests to kill those mutants:
- assert Accept-Crs / Content-Crs are EPSG:4326,
- assert OpenZaakAsync rejects a null request/registration without calling out,
- assert a non-2xx response throws and an empty body throws InvalidOperationException,
- decode the Bearer token and assert the HS256 header + acl identity claims.

Raises the ACL mutation score to 95%. The one remaining survivor mutates only
the exception *message* text (an equivalent mutant — message strings are not
worth a brittle assertion).

Refs #47.

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

services/acl/Acl.Tests/AclServiceTests.cs

@@ -44,4 +44,21 @@ public class AclServiceTests
         Assert.Equal(defaults.ZaaktypeUrl, req.Zaaktype);
         Assert.Equal(new DateOnly(2026, 6, 4), req.Startdatum);
     }
+
+    [Fact]
+    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"),
+        };
+        var service = new AclService(gateway, defaults, new FixedClock(new DateOnly(2026, 6, 4)));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(() => service.OpenZaakAsync(null!));
+        Assert.Null(gateway.Captured);
+    }
 }

services/acl/Acl.Tests/OpenZaakGatewayTests.cs

@@ -1,5 +1,7 @@
 using System.Net;
 using System.Net.Http.Json;
+using System.Text;
+using System.Text.Json;
 using Acl.Application;
 using Acl.Infrastructure;
 
@@ -14,38 +16,120 @@ public class OpenZaakGatewayTests
             => onSend(request);
     }
 
-    [Fact]
+    private static OpenZaakGateway Gateway(StubHandler handler) => new(
-    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
+        new HttpClient(handler),
+        new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });
+
+    private static ZaakRequest SampleRequest() => new(
+        "517439943", "517439943", "openbaar",
+        new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
+
+    private static StubHandler Created(out RequestCapture capture)
     {
-        HttpRequestMessage? seen = null;
+        var c = new RequestCapture();
-        string? body = null;
+        capture = c;
-        var handler = new StubHandler(async req =>
+        return new StubHandler(async req =>
         {
-            seen = req;
+            c.Seen = req;
-            body = await req.Content!.ReadAsStringAsync();
+            c.Body = req.Content is null ? null : await req.Content.ReadAsStringAsync();
             return new HttpResponseMessage(HttpStatusCode.Created)
             {
                 Content = JsonContent.Create(new { url = "http://openzaak/zaken/api/v1/zaken/xyz" }),
             };
         });
-        var gateway = new OpenZaakGateway(
+    }
-            new HttpClient(handler),
-            new OpenZaakOptions { BaseUrl = new("http://openzaak"), ClientId = "cid", Secret = "sec" });
-        var request = new ZaakRequest(
-            "517439943", "517439943", "openbaar",
-            new("http://openzaak/catalogi/api/v1/zaaktypen/big"), new DateOnly(2026, 6, 4));
 
-        var url = await gateway.OpenZaakAsync(request);
+    private sealed class RequestCapture
+    {
+        public HttpRequestMessage? Seen;
+        public string? Body;
+    }
+
+    [Fact]
+    public async Task Posts_zaak_to_openzaak_with_bearer_and_default_fields_and_returns_url()
+    {
+        var handler = Created(out var capture);
+
+        var url = await Gateway(handler).OpenZaakAsync(SampleRequest());
 
         Assert.Equal("http://openzaak/zaken/api/v1/zaken/xyz", url.ToString());
-        Assert.Equal(HttpMethod.Post, seen!.Method);
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
-        Assert.Equal("http://openzaak/zaken/api/v1/zaken", seen.RequestUri!.ToString());
+        Assert.Equal("http://openzaak/zaken/api/v1/zaken", capture.Seen.RequestUri!.ToString());
-        Assert.Equal("Bearer", seen.Headers.Authorization!.Scheme);
+        Assert.Equal("Bearer", capture.Seen.Headers.Authorization!.Scheme);
-        Assert.False(string.IsNullOrWhiteSpace(seen.Headers.Authorization.Parameter));
+        Assert.False(string.IsNullOrWhiteSpace(capture.Seen.Headers.Authorization.Parameter));
-        Assert.Contains("\"bronorganisatie\":\"517439943\"", body);
+        Assert.Contains("\"bronorganisatie\":\"517439943\"", capture.Body);
-        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", body);
+        Assert.Contains("\"verantwoordelijkeOrganisatie\":\"517439943\"", capture.Body);
-        Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", body);
+        Assert.Contains("\"vertrouwelijkheidaanduiding\":\"openbaar\"", capture.Body);
-        Assert.Contains("\"startdatum\":\"2026-06-04\"", body);
+        Assert.Contains("\"startdatum\":\"2026-06-04\"", capture.Body);
-        Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", body);
+        Assert.Contains("\"zaaktype\":\"http://openzaak/catalogi/api/v1/zaaktypen/big\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Sends_the_geo_crs_headers_required_by_the_zaken_api()
+    {
+        var handler = Created(out var capture);
+
+        await Gateway(handler).OpenZaakAsync(SampleRequest());
+
+        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen!.Headers.GetValues("Accept-Crs")));
+        Assert.Equal("EPSG:4326", Assert.Single(capture.Seen.Content!.Headers.GetValues("Content-Crs")));
+    }
+
+    [Fact]
+    public async Task Mints_a_hs256_jwt_carrying_the_acl_identity_claims()
+    {
+        var handler = Created(out var capture);
+
+        await Gateway(handler).OpenZaakAsync(SampleRequest());
+
+        var parts = capture.Seen!.Headers.Authorization!.Parameter!.Split('.');
+        Assert.Equal(3, parts.Length);
+        using var header = JsonDocument.Parse(DecodeSegment(parts[0]));
+        Assert.Equal("HS256", header.RootElement.GetProperty("alg").GetString());
+        Assert.Equal("JWT", header.RootElement.GetProperty("typ").GetString());
+        using var payload = JsonDocument.Parse(DecodeSegment(parts[1]));
+        Assert.Equal("cid", payload.RootElement.GetProperty("client_id").GetString());
+        Assert.Equal("acl", payload.RootElement.GetProperty("user_id").GetString());
+        Assert.Equal("acl", payload.RootElement.GetProperty("user_representation").GetString());
+    }
+
+    [Fact]
+    public async Task Throws_when_openzaak_rejects_the_request()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.BadRequest)));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
+    }
+
+    [Fact]
+    public async Task Throws_when_openzaak_returns_an_empty_body()
+    {
+        var handler = new StubHandler(_ =>
+            Task.FromResult(new HttpResponseMessage(HttpStatusCode.Created)
+            {
+                Content = new StringContent("null", Encoding.UTF8, "application/json"),
+            }));
+
+        await Assert.ThrowsAsync<InvalidOperationException>(
+            () => Gateway(handler).OpenZaakAsync(SampleRequest()));
+    }
+
+    [Fact]
+    public async Task Rejects_a_null_request()
+    {
+        var handler = new StubHandler(_ => throw new InvalidOperationException("should not be sent"));
+
+        await Assert.ThrowsAsync<ArgumentNullException>(
+            () => Gateway(handler).OpenZaakAsync(null!));
+    }
+
+    // ZGW tokens are base64url with padding stripped (ZgwToken.B64Url); restore it to decode.
+    private static string DecodeSegment(string segment)
+    {
+        var b64 = segment.Replace('-', '+').Replace('_', '/');
+        b64 = (b64.Length % 4) switch { 2 => b64 + "==", 3 => b64 + "=", _ => b64 };
+        return Encoding.UTF8.GetString(Convert.FromBase64String(b64));
     }
 }