Add controller spec to ensure lead image markdown isn't in body

This does 2 things:

1. updates the vaidation that checks for the markdown for a lead image
not being in the body to use the edition_lead_image rather than the
lead_image association. The lead image association returns nil until
persisted. We need to make sure the built edition_lead_image is valid.
2. adds a controller spec to ensure that update endpoint fails with
a relevant error message when a user tries to make an image the lead
image with it's markdown in the body.

app/models/edition/custom_lead_image.rb

@@ -34,12 +34,12 @@ def remove_lead_image
   end
 
   def body_does_not_contain_lead_image
-    return if lead_image.blank? || images.none?
+    return if edition_lead_image.blank? || images.none?
 
     html = Whitehall::GovspeakRenderer.new.govspeak_edition_to_html(self)
     doc = Nokogiri::HTML::DocumentFragment.parse(html)
 
-    if doc.css("img").any? { |img| img[:src] == lead_image.url }
+    if doc.css("img").any? { |img| img[:src] == edition_lead_image.image.url }
       errors.add(:body, "cannot have a reference to the lead image in the text")
     end
   end

test/functional/admin/edition_lead_images_controller_test.rb

@@ -20,7 +20,7 @@ class Admin::EditionLeadImagesControllerTest < ActionController::TestCase
     assert_equal "Lead image updated to minister-of-funk.960x640.jpg", flash[:notice]
   end
 
-  test "PATCH :update does not update the lead image when the edition is invalid " do
+  test "PATCH :update does not update the lead image when the edition is invalid" do
     login_as :writer
 
     published_edition = create(:published_case_study)
@@ -41,6 +41,24 @@ class Admin::EditionLeadImagesControllerTest < ActionController::TestCase
     assert_equal "This edition is invalid: Change note can't be blank", flash[:alert]
   end
 
+  test "PATCH :update does not update the lead image when edition's body contains the images markdown" do
+    login_as :writer
+
+    published_edition = create(:published_case_study)
+    image = build(:image)
+    edition = create(:draft_case_study, images: [image], document: published_edition.document, body: "!!1")
+
+    Whitehall::PublishingApi
+    .expects(:save_draft)
+    .never
+
+    get :update, params: { edition_id: edition.id, id: image.id }
+
+    assert_nil edition.reload.lead_image
+    assert_redirected_to admin_edition_images_path(edition)
+    assert_equal "This edition is invalid: Body cannot have a reference to the lead image in the text", flash[:alert]
+  end
+
   test "PATCH :update forbids unauthorised users" do
     login_as :world_editor
     image = build(:image)