test(workflow): user-task client — werkbak query, claim, complete beoordeling (refs #13)

Red — GetOpenBeoordelingenAsync/ClaimAsync/CompleteBeoordelingAsync do not exist yet.

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

services/domain/Big.Tests/FlowableWorkflowClientTests.cs

@@ -1,5 +1,6 @@
 using System.Net;
 using System.Text;
+using Big.Application;
 using Big.Domain;
 using Big.Infrastructure;
 
@@ -136,4 +137,106 @@ public class FlowableWorkflowClientTests
         await Assert.ThrowsAsync<HttpRequestException>(
             () => client.CompleteOpenZaakJobAsync("job-1", new Uri("http://openzaak/zaken/api/v1/zaken/abc")));
     }
+
+    // ── S-12b: behandelaar user tasks (werkbak / claim / complete) ────────────────────────────────
+
+    [Fact]
+    public async Task Open_beoordelingen_queries_beoordelen_tasks_with_their_registration_id()
+    {
+        var rid = RegistrationId.New();
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK,
+            $$"""
+            {"data":[{"id":"task-1","processVariables":[{"name":"registrationId","type":"string","value":"{{rid}}"}]}],"total":1}
+            """));
+
+        var tasks = await client.GetOpenBeoordelingenAsync();
+
+        var task = Assert.Single(tasks);
+        Assert.Equal("task-1", task.TaskId);
+        Assert.Equal(rid, task.RegistrationId);
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://flowable/flowable-rest/service/runtime/tasks/query",
+            capture.Seen.RequestUri!.ToString());
+        Assert.Equal("rest-admin:test", DecodeBasic(capture.Seen));
+        Assert.Contains("\"processDefinitionKey\":\"registratie\"", capture.Body);
+        Assert.Contains("\"taskDefinitionKey\":\"Beoordelen\"", capture.Body);
+        Assert.Contains("\"includeProcessVariables\":true", capture.Body);
+    }
+
+    [Theory]
+    [InlineData("""{"data":[],"total":0}""")]
+    [InlineData("""{"data":null,"total":0}""")]
+    public async Task Open_beoordelingen_is_empty_when_no_tasks_are_waiting(string body)
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK, body));
+
+        Assert.Empty(await client.GetOpenBeoordelingenAsync());
+        Assert.NotNull(capture.Seen);
+    }
+
+    [Fact]
+    public async Task Open_beoordelingen_throws_when_a_task_carries_no_registration_id()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK,
+            """{"data":[{"id":"task-1","processVariables":[]}],"total":1}"""));
+
+        var ex = await Assert.ThrowsAsync<InvalidOperationException>(() => client.GetOpenBeoordelingenAsync());
+        Assert.Contains("task-1", ex.Message);
+        Assert.Contains("registrationId", ex.Message);
+    }
+
+    [Fact]
+    public async Task Claim_assigns_the_task_to_the_behandelaar()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK));
+
+        await client.ClaimAsync("task-1", "merel-behandelaar");
+
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://flowable/flowable-rest/service/runtime/tasks/task-1",
+            capture.Seen.RequestUri!.ToString());
+        Assert.Contains("\"action\":\"claim\"", capture.Body);
+        Assert.Contains("\"assignee\":\"merel-behandelaar\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Claim_throws_when_flowable_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.Conflict));
+
+        await Assert.ThrowsAsync<HttpRequestException>(() => client.ClaimAsync("task-1", "merel-behandelaar"));
+    }
+
+    [Theory]
+    [InlineData(BeoordelingsBesluit.Goedkeuren, "goedkeuren")]
+    [InlineData(BeoordelingsBesluit.Afwijzen, "afwijzen")]
+    public async Task Complete_posts_the_besluit_variable_to_the_task(BeoordelingsBesluit besluit, string expected)
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.OK));
+
+        await client.CompleteBeoordelingAsync("task-1", besluit);
+
+        Assert.Equal(HttpMethod.Post, capture.Seen!.Method);
+        Assert.Equal("http://flowable/flowable-rest/service/runtime/tasks/task-1",
+            capture.Seen.RequestUri!.ToString());
+        Assert.Contains("\"action\":\"complete\"", capture.Body);
+        Assert.Contains("\"name\":\"besluit\"", capture.Body);
+        Assert.Contains($"\"value\":\"{expected}\"", capture.Body);
+    }
+
+    [Fact]
+    public async Task Complete_beoordeling_throws_when_flowable_rejects_the_request()
+    {
+        var capture = new RequestCapture();
+        var client = Client(capture.Responds(HttpStatusCode.InternalServerError));
+
+        await Assert.ThrowsAsync<HttpRequestException>(
+            () => client.CompleteBeoordelingAsync("task-1", BeoordelingsBesluit.Goedkeuren));
+    }
 }