D1-18: HomeItemProtection — Home menu item cannot be moved, reordered, or deleted

test/bds/desktop/menu_editor/home_item_protection_test.exs

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+defmodule BDS.Desktop.MenuEditor.HomeItemProtectionTest do
+  use ExUnit.Case, async: true
+
+  alias BDS.Desktop.ShellLive.MenuEditor.{TreeOps, TreePredicates}
+
+  @home_id TreeOps.home_item_id()
+  @other_id "some-other-item"
+
+  defp home_state do
+    %{
+      items: [
+        TreeOps.home_item(),
+        %{item_id: @other_id, kind: :page, label: "About", slug: "about", children: [], is_home: false}
+      ],
+      selected_id: @home_id,
+      draft: nil
+    }
+  end
+
+  defp other_state do
+    %{
+      items: [
+        TreeOps.home_item(),
+        %{item_id: @other_id, kind: :page, label: "About", slug: "about", children: [], is_home: false}
+      ],
+      selected_id: @other_id,
+      draft: nil
+    }
+  end
+
+  describe "TreePredicates" do
+    test "can_move_up? returns false for home item" do
+      items = home_state().items
+      refute TreePredicates.can_move_up?(items, @home_id)
+    end
+
+    test "can_move_down? returns false for home item" do
+      items = home_state().items
+      refute TreePredicates.can_move_down?(items, @home_id)
+    end
+
+    test "can_indent? returns false for home item" do
+      items = home_state().items
+      refute TreePredicates.can_indent?(items, @home_id)
+    end
+
+    test "can_unindent? returns false for home item" do
+      items = home_state().items
+      refute TreePredicates.can_unindent?(items, @home_id)
+    end
+
+    test "can_delete? returns false for home item" do
+      refute TreePredicates.can_delete?(@home_id)
+    end
+
+    test "can_delete? returns true for non-home item" do
+      assert TreePredicates.can_delete?(@other_id)
+    end
+  end
+
+  describe "TreeOps" do
+    test "move_selected is no-op when home item is selected" do
+      state = home_state()
+      assert TreeOps.move_selected(state, :up) == state
+      assert TreeOps.move_selected(state, :down) == state
+    end
+
+    test "move_selected works for non-home item" do
+      state = other_state()
+      moved = TreeOps.move_selected(state, :up)
+      assert moved != state
+    end
+
+    test "indent_selected is no-op when home item is selected" do
+      state = home_state()
+      assert TreeOps.indent_selected(state) == state
+    end
+
+    test "unindent_selected is no-op when home item is selected" do
+      state = home_state()
+      assert TreeOps.unindent_selected(state) == state
+    end
+
+    test "delete_selected is no-op when home item is selected" do
+      state = home_state()
+      assert TreeOps.delete_selected(state) == state
+    end
+
+    test "drop_selected is no-op when drag item is home item" do
+      state = other_state()
+      assert TreeOps.drop_selected(state, @home_id, @other_id, "after") == state
+    end
+
+    test "drop_selected works when neither item is home" do
+      state = %{
+        other_state()
+        | items: [
+            %{item_id: "a", kind: :page, label: "A", slug: "a", children: [], is_home: false},
+            %{item_id: "b", kind: :page, label: "B", slug: "b", children: [], is_home: false}
+          ],
+          selected_id: "b"
+      }
+
+      dropped = TreeOps.drop_selected(state, "a", "b", "before")
+      assert dropped != state
+    end
+  end
+end