read photo from a harvest's planting

app/models/harvest.rb

@@ -74,6 +74,10 @@ class Harvest < ApplicationRecord
     harvested_at - planting.planted_at
   end
 
+  def default_photo
+    most_liked_photo || planting&.default_photo
+  end
+
   # we're storing the harvest weight in kilograms in the db too
   # to make data manipulation easier
   def set_si_weight

spec/models/harvest_spec.rb

@@ -237,6 +237,7 @@ describe Harvest do
           @planting = FactoryBot.create(:planting, crop: @harvest.crop)
           @photo = FactoryBot.create(:photo, owner: @planting.owner)
           @planting.photos << @photo
+          @harvest.update(planting: @planting)
         end
 
         it 'has a default photo' do