Fix optionality

app/models/case_log.rb

@@ -186,8 +186,8 @@ class CaseLog < ApplicationRecord
     previous_la_known == 1
   end
 
-  def tshortfall_known?
+  def tshortfall_unknown?
-    !!(tshortfall_known && tshortfall_known.zero?)
+    tshortfall_known == 1
   end
 
   def is_secure_tenancy?
@@ -433,7 +433,7 @@ private
 
   def dynamically_not_required
     previous_la_known_field = postcode_known? ? %w[previous_la_known] : []
-    tshortfall_field = tshortfall_known? ? [] : %w[tshortfall]
+    tshortfall_field = tshortfall_unknown? ? %w[tshortfall] : []
     previous_la_known_field + tshortfall_field
   end
 

spec/models/case_log_spec.rb

@@ -1771,6 +1771,32 @@ RSpec.describe CaseLog do
     end
   end
 
+  describe "tshortfall_unknown?" do
+    context "when tshortfall is nil" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: nil) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be false
+      end
+    end
+
+    context "when tshortfall is No" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: 1) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be true
+      end
+    end
+
+    context "when tshortfall is Yes" do
+      let(:case_log) { FactoryBot.create(:case_log, :in_progress, tshortfall_known: 0) }
+
+      it "returns false" do
+        expect(case_log.tshortfall_unknown?).to be false
+      end
+    end
+  end
+
   describe "paper trail" do
     let(:case_log) { FactoryBot.create(:case_log, :in_progress) }