Add validation for item_type

This ensures that item_types only have values that are defined in the
config, as well as ensures they cannot be changed once persisted.

app/models/object_store/item.rb

@@ -4,6 +4,10 @@ class Item < Edition
 
     after_initialize :add_field_accessors
 
+    validates :item_type, presence: true, on: :create
+    validate :item_type_cannot_change
+    validates :item_type, inclusion: { in: ObjectStore.item_types }
+
     def summary_required?
       false
     end
@@ -29,5 +33,11 @@ def add_field_accessors
     rescue UnknownItemType
       # Ignored
     end
+
+    def item_type_cannot_change
+      if persisted? && item_type_changed?
+        errors.add :item_type, "cannot be changed after creation"
+      end
+    end
   end
 end

test/unit/app/models/object_store/item_test.rb

@@ -27,4 +27,26 @@ class ObjectStore::ItemTest < ActiveSupport::TestCase
   test "#previously_published returns false" do
     assert_equal @item.previously_published, false
   end
+
+  test "item_type is required" do
+    item = build(:object_store_item, item_type: nil)
+    assert_not item.valid?
+    assert item.errors[:item_type].any?
+  end
+
+  test "item_type cannot be changed" do
+    @item.email_address = "[email protected]"
+    @item.save!
+
+    @item.item_type = "foo"
+    assert_not @item.valid?
+    assert @item.errors[:item_type].include?("cannot be changed after creation")
+  end
+
+  test "item_type must be valid" do
+    item = build(:object_store_item, item_type: "banana")
+
+    assert_not item.valid?
+    assert item.errors[:item_type].any?
+  end
 end