From 9dcb673139f56ea65a17cd5864987e87c4084f19 Mon Sep 17 00:00:00 2001
From: Matt Beanland <beanland@live.com.au>
Date: Fri, 22 May 2026 22:12:50 +0930
Subject: [PATCH] test case shows bug fixed

---
 .../extension/characteristic_test.exs         | 31 +++++++++++++++++++
 1 file changed, 31 insertions(+)

diff --git a/test/provider/extension/characteristic_test.exs b/test/provider/extension/characteristic_test.exs
index 06dbad2..864b331 100644
--- a/test/provider/extension/characteristic_test.exs
+++ b/test/provider/extension/characteristic_test.exs
@@ -7,6 +7,7 @@ defmodule Diffo.Provider.Extension.CharacteristicTest do
   use ExUnit.Case, async: true
   @moduletag :domain_extended
   alias Diffo.Test.Parties
+  alias Diffo.Test.Servo
 
   setup do
     AshNeo4j.Sandbox.checkout()
@@ -23,4 +24,34 @@ defmodule Diffo.Provider.Extension.CharacteristicTest do
       assert Diffo.Unwrap.unwrap(shelves) == []
     end
   end
+
+  # Regression coverage for issue #62 — invalid keys or invalid value types
+  # supplied to a typed characteristic update must surface an error rather than
+  # being silently dropped or persisted as-is.
+  describe "typed characteristic update validation (#62)" do
+    test "valid update succeeds" do
+      {:ok, shelf} = Parties.build_shelf_with_installer()
+
+      updates = [shelf: [family: :ISAM, model: "EBLT48", technology: :adsl2Plus]]
+
+      assert {:ok, _} = Servo.define_shelf(shelf, %{characteristic_value_updates: updates})
+    end
+
+    test "unknown field is rejected" do
+      {:ok, shelf} = Parties.build_shelf_with_installer()
+
+      updates = [shelf: [family: :ISAM, cvc_id: "CVC-POI-SYD-001"]]
+
+      assert {:error, _} = Servo.define_shelf(shelf, %{characteristic_value_updates: updates})
+    end
+
+    test "invalid value type is rejected" do
+      {:ok, shelf} = Parties.build_shelf_with_installer()
+
+      # :family is :atom — a bare map cannot be cast to an atom
+      updates = [shelf: [family: %{not: :an_atom}]]
+
+      assert {:error, _} = Servo.define_shelf(shelf, %{characteristic_value_updates: updates})
+    end
+  end
 end