Add spec for poll model (#23399)

Co-authored-by: Nick Schonning <nschonni@gmail.com>
Co-authored-by: Claire <claire.github-309c@sitedethib.com>

spec/models/poll_spec.rb

@@ -29,4 +29,23 @@ describe Poll do
       end
     end
   end
+
+  describe 'validations' do
+    context 'when valid' do
+      let(:poll) { Fabricate.build(:poll) }
+
+      it 'is valid with valid attributes' do
+        expect(poll).to be_valid
+      end
+    end
+
+    context 'when not valid' do
+      let(:poll) { Fabricate.build(:poll, expires_at: nil) }
+
+      it 'is invalid without an expire date' do
+        poll.valid?
+        expect(poll).to model_have_error_on_field(:expires_at)
+      end
+    end
+  end
 end