Check CKEditor is filled properly in tests

It looks like sometimes, particularly when the first thing we do after
loading a page is filling the CKEditor fields and submitting the form,
CKEditor doesn't have enough time to format the text, and so it's sent
as plain text instead of HTML. This behaviour can be reproduced on my
local machine after upgrading to Rails 5.1, with the test "Admin Active
polls Add" failing 100% of the time.

Checking CKEditor has been filled in correctly solves the issue.

spec/features/admin/legislation/processes_spec.rb

@@ -264,10 +264,7 @@ describe "Admin collaborative legislation" do
       expect(page).not_to have_link "Remove language"
       expect(page).not_to have_field "translation_locale"
 
-      within(".translatable-fields[data-locale='en']") do
-        fill_in_ckeditor find("textarea", visible: false)[:id],
-                         with: "There is still a long journey ahead of us"
-      end
+      fill_in_ckeditor "Summary", with: "There is still a long journey ahead of us"
 
       click_button "Update Process"
 

spec/shared/features/nested_documentable.rb

@@ -351,7 +351,7 @@ end
 
 def documentable_fill_new_valid_dashboard_action
   fill_in :dashboard_action_title, with: "Dashboard title"
-  fill_in_ckeditor :dashboard_action_description, with: "Dashboard description"
+  fill_in_ckeditor "Description", with: "Dashboard description"
 end
 
 def documentable_fill_new_valid_budget_investment

spec/support/common_actions/verifications.rb

@@ -44,10 +44,9 @@ module Verifications
     end
   end
 
-  # @param [String] locator label text for the textarea or textarea id
-  def fill_in_ckeditor(locator, params = {})
-    # Find out ckeditor id at runtime using its label
-    locator = find("label", text: locator)[:for] if page.has_css?("label", text: locator)
+  def fill_in_ckeditor(text, params = {})
+    locator = find("label", text: text)[:for]
+
     # Fill the editor content
     page.execute_script <<-SCRIPT
         var ckeditor = CKEDITOR.instances.#{locator}
@@ -55,5 +54,7 @@ module Verifications
         ckeditor.focus()
         ckeditor.updateElement()
     SCRIPT
+
+    expect(page).to have_ckeditor text, with: params[:with]
   end
 end