test(friend): end-to-end multi-viewer apply→approve→friendship flow

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

SVSim.UnitTests/Controllers/FriendControllerTests.cs

@@ -284,4 +284,54 @@ public class FriendControllerTests
         var response = await client.PostAsync("/friend/info", JsonBody("{}"));
         Assert.That(response.StatusCode, Is.EqualTo(HttpStatusCode.Unauthorized));
     }
+
+    [Test]
+    public async Task Multi_viewer_flow_A_sends_B_approves_both_see_friend()
+    {
+        using var factory = new SVSimTestFactory();
+        long viewerA = await SeedViewer(factory, 76_561_198_000_020_001UL, "Alice");
+        long viewerB = await SeedViewer(factory, 76_561_198_000_020_002UL, "Bob");
+
+        // A sends apply to B.
+        using (var clientA = factory.CreateAuthenticatedClient(viewerA))
+        {
+            var resp = await clientA.PostAsync("/friend/send_apply", JsonBody($$"""{"friend_id":{{(int)viewerB}}}"""));
+            Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+        }
+
+        // B sees the apply in receive_apply_info.
+        int applyId;
+        using (var clientB = factory.CreateAuthenticatedClient(viewerB))
+        {
+            var resp = await clientB.PostAsync("/friend/receive_apply_info", JsonBody("{}"));
+            var raw = await resp.Content.ReadAsStringAsync();
+            using var doc = JsonDocument.Parse(raw);
+            var applies = doc.RootElement.GetProperty("receive_applies");
+            Assert.That(applies.GetArrayLength(), Is.EqualTo(1));
+            applyId = applies[0].GetProperty("id").GetInt32();
+            Assert.That(applies[0].GetProperty("name").GetString(), Is.EqualTo("Alice"));
+        }
+
+        // B approves.
+        using (var clientB = factory.CreateAuthenticatedClient(viewerB))
+        {
+            var resp = await clientB.PostAsync("/friend/approve_apply", JsonBody($$"""{"apply_id":{{applyId}}}"""));
+            Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+        }
+
+        // Both A and B now see each other in /friend/info.
+        async Task<string> GetFriendName(long ownerId)
+        {
+            using var client = factory.CreateAuthenticatedClient(ownerId);
+            var resp = await client.PostAsync("/friend/info", JsonBody("{}"));
+            var raw = await resp.Content.ReadAsStringAsync();
+            using var doc = JsonDocument.Parse(raw);
+            var friends = doc.RootElement.GetProperty("friends");
+            Assert.That(friends.GetArrayLength(), Is.EqualTo(1));
+            return friends[0].GetProperty("name").GetString()!;
+        }
+
+        Assert.That(await GetFriendName(viewerA), Is.EqualTo("Bob"));
+        Assert.That(await GetFriendName(viewerB), Is.EqualTo("Alice"));
+    }
 }