feat: add test

spec/models/lettings_log_spec.rb

@@ -2035,6 +2035,21 @@ RSpec.describe LettingsLog do
         allow(FormHandler.instance).to receive(:get_form).and_return(real_2021_2022_form)
       end
 
+      describe "when changing a log's scheme and hence calling reset_scheme_location!" do
+        let!(:scheme) { FactoryBot.create(:scheme)}
+        let!(:invalid_location_1) { FactoryBot.create(:location, scheme:, startdate: Time.zone.today + 3.weeks)}
+        let!(:valid_location) { FactoryBot.create(:location, scheme:, startdate: Time.zone.yesterday)}
+        let!(:invalid_location_2) { FactoryBot.create(:location, scheme:, startdate: Time.zone.today + 3.weeks)}
+
+        context "when there is one valid location and many invalid locations in the new scheme" do
+          let(:log) { create(:lettings_log, scheme: nil, location_id: nil, startdate: Time.zone.today) }
+
+          it "infers that the log is for the valid location" do
+            expect{ log.update!(scheme:) }.to change(log, :location_id).from(nil).to(valid_location.id)
+          end
+        end
+      end
+
       context "and a scheme with a single log is selected" do
         let(:scheme) { create(:scheme) }
         let!(:location) { create(:location, scheme:) }