Make the interpolated collection validation accept exactly one saved scenario.

app/models/collection.rb

@@ -176,10 +176,10 @@ def validate_scenario_versions
   end
 
   def validate_interpolated
-    # Ensure interpolated collections (AKA transition paths) have no saved scenarios
+    # Ensure interpolated collections (AKA transition paths) have one saved scenario
     active_saved_scenarios = collection_saved_scenarios.reject(&:marked_for_destruction?)
-    if self.interpolated? && active_saved_scenarios.size > 1
-      errors.add(:scenarios, "interpolated collections cannot have more than 1 saved scenario")
+    if self.interpolated? && active_saved_scenarios.size != 1
+      errors.add(:scenarios, "interpolated collections must have exactly 1 saved scenario")
     end
   end
 

spec/factories/collection.rb

@@ -7,17 +7,28 @@
     title { 'My Collection' }
     end_year { 2050 }
     version { Version.find_by(tag: "latest") }
+    interpolation { false }
 
     transient do
       scenarios_count { 2 }
+      saved_scenarios_count { interpolation ? 1 : 0 }
     end
 
-    after(:create) do |myc, evaluator|
-      create_list(
-        :collection_scenario,
-        evaluator.scenarios_count,
-        collection: myc
-      )
+    after(:build) do |collection, evaluator|
+      evaluator.scenarios_count.times do
+        collection.scenarios << build(
+          :collection_scenario,
+          collection: collection
+        )
+      end
+
+      evaluator.saved_scenarios_count.times do
+        collection.collection_saved_scenarios << build(
+          :collection_saved_scenario,
+          collection: collection,
+          user: collection.user
+        )
+      end
     end
   end
 

spec/factories/collection_saved_scenario.rb

@@ -2,7 +2,11 @@
 
 FactoryBot.define do
   factory :collection_saved_scenario do
-    saved_scenario
+    transient do
+      user { nil }
+    end
+
+    saved_scenario { create(:saved_scenario, user: user) }
     collection
   end
 end

spec/models/collection_spec.rb

@@ -68,7 +68,7 @@
 
   describe 'number of scenarios' do
     let(:user) { create(:user) }
-    let(:myc) { create(:collection, user: user, scenarios_count: 7) }
+    let(:myc) { create(:collection, user: user, scenarios_count: 6) }
 
     context 'with more than 6 combined scenarios' do
       before do
@@ -77,7 +77,7 @@
       end
 
       it 'is not valid' do
-        expect(myc).not_to be_valid
+        expect(myc.reload).not_to be_valid
       end
     end
   end

spec/requests/api/collections_spec.rb

@@ -151,7 +151,8 @@
         end_year: 2050,
         scenario_ids: [1, 2, 3],
         title: 'My collection',
-        version: Version.default.tag
+        version: Version.default.tag,
+        interpolation: false
       }
     end
 
@@ -440,7 +441,7 @@
       it 'does not insert a saved_scenario' do
         expect { request }.not_to change { collection.reload.latest_scenario_ids }
         expect(response).to have_http_status(:unprocessable_entity)
-        expect(JSON.parse(response.body)['scenarios']).to include('interpolated collections cannot have more than 1 saved scenario')
+        expect(JSON.parse(response.body)['scenarios']).to include('interpolated collections must have exactly 1 saved scenario')
       end
     end
 

spec/services/api/create_collection_spec.rb

@@ -12,7 +12,8 @@
       area_code: 'nl2019',
       end_year: 2050,
       scenario_ids: [10, 20],
-      version: Version.default.tag
+      version: Version.default.tag,
+      interpolation: false
     }
   end