diff --git a/SVSim.UnitTests/Wire/FriendInfoWireShape.cs b/SVSim.UnitTests/Wire/FriendInfoWireShape.cs
new file mode 100644
index 0000000..3240cd6
--- /dev/null
+++ b/SVSim.UnitTests/Wire/FriendInfoWireShape.cs
@@ -0,0 +1,58 @@
+using System.Text.Json;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Friend;
+
+namespace SVSim.UnitTests.Wire;
+
+public class FriendInfoWireShape
+{
+    [Test]
+    public void FriendEntryDto_serialization_matches_prod_capture()
+    {
+        // Mirrors the prod capture's first `friends[]` entry from
+        // data_dumps/captures/traffic_prod_misc_clicking.ndjson (gigapurin).
+        var entry = new FriendEntryDto
+        {
+            DeviceType = "2",
+            Name = "gigapurin",
+            CountryCode = "USA",
+            MaxFriend = "20",
+            LastPlayTime = "2024-10-31 03:16:37",
+            IsReceivedTwoPickMission = "1",
+            Birth = "0",
+            MissionChangeTime = "2017-09-15 02:36:09",
+            MissionReceiveType = "0",
+            IsOfficial = "0",
+            IsOfficialMarkDisplayed = "0",
+            ViewerId = 283562639,
+            Rank = 11,
+            EmblemId = 900311010,
+            DegreeId = 300003,
+        };
+
+        var options = new JsonSerializerOptions
+        {
+            PropertyNamingPolicy = JsonNamingPolicy.SnakeCaseLower,
+            DefaultIgnoreCondition = System.Text.Json.Serialization.JsonIgnoreCondition.WhenWritingNull,
+        };
+        var json = JsonSerializer.Serialize(entry, options);
+
+        var expected =
+            "{\"device_type\":\"2\"," +
+            "\"name\":\"gigapurin\"," +
+            "\"country_code\":\"USA\"," +
+            "\"max_friend\":\"20\"," +
+            "\"last_play_time\":\"2024-10-31 03:16:37\"," +
+            "\"is_received_two_pick_mission\":\"1\"," +
+            "\"birth\":\"0\"," +
+            "\"mission_change_time\":\"2017-09-15 02:36:09\"," +
+            "\"mission_receive_type\":\"0\"," +
+            "\"is_official\":\"0\"," +
+            "\"is_official_mark_displayed\":\"0\"," +
+            "\"viewer_id\":283562639," +
+            "\"rank\":11," +
+            "\"emblem_id\":900311010," +
+            "\"degree_id\":300003}";
+
+        Assert.That(json, Is.EqualTo(expected));
+    }
+}