Don't delegate preview methods to controller. (#9097)

The controller will try to load the Election from the params but when
rendering an election that's the single one in a voting there are no
params. Instead, it's better to use the model in the cell.

decidim-elections/app/cells/decidim/elections/election_vote_cta_cell.rb

@@ -5,15 +5,20 @@ module Elections
     # This cell renders the results
     # for a given instance of an Election
     class ElectionVoteCtaCell < Decidim::ViewModel
+      include Decidim::Elections::HasVoteFlow
+
       delegate :current_user,
                :current_participatory_space,
-               :preview_mode?,
-               :can_preview?,
-               :vote_flow,
+               :allowed_to?,
                to: :controller
 
       private
 
+      # This is needed by HasVoteFlow
+      def election
+        model
+      end
+
       def last_vote
         @last_vote ||= Decidim::Elections::Votes::LastVoteForVoter.for(model, vote_flow.voter_id) if vote_flow.has_voter?
       end

decidim-elections/spec/system/homepage_content_blocks_spec.rb

@@ -6,21 +6,35 @@
   let(:organization) { create(:organization) }
   let(:show_statistics) { true }
   let!(:promoted_voting) { create(:voting, :promoted, organization: organization) }
-  let!(:unpromoted_voting) { create(:voting, organization: organization) }
-  let!(:promoted_external_voting) { create(:voting, :promoted) }
 
   before do
     create :content_block, organization: organization, scope_name: :homepage, manifest_name: :highlighted_votings
     switch_to_host(organization.host)
   end
 
-  it "includes active votings to the homepage" do
-    visit decidim.root_path
+  context "when there are multiple votings" do
+    let!(:unpromoted_voting) { create(:voting, organization: organization) }
+    let!(:promoted_external_voting) { create(:voting, :promoted) }
+
+    it "includes active votings to the homepage" do
+      visit decidim.root_path
+
+      within "#highlighted-votings" do
+        expect(page).to have_i18n_content(promoted_voting.title)
+        expect(page).to have_i18n_content(unpromoted_voting.title)
+        expect(page).not_to have_i18n_content(promoted_external_voting.title)
+      end
+    end
+  end
+
+  context "when there's only one voting" do
+    it "redirects to the voting page" do
+      visit decidim.root_path
+      click_link "Votings"
 
-    within "#highlighted-votings" do
       expect(page).to have_i18n_content(promoted_voting.title)
-      expect(page).to have_i18n_content(unpromoted_voting.title)
-      expect(page).not_to have_i18n_content(promoted_external_voting.title)
+      expect(page).to have_i18n_content(promoted_voting.description)
+      expect(page).to have_current_path(decidim_votings.voting_path(promoted_voting))
     end
   end
 end