Add test for JSON derived and dependent on false options

spec/fixtures/forms/2022_2023.json

@@ -94,6 +94,29 @@
                     "width": 10
                   }
                 }
+              },
+              "outstanding_amount_known": {
+                "header": "",
+                "description": "",
+                "questions": {
+                  "tshortfall_known": {
+                    "check_answer_label": "",
+                    "header": "",
+                    "hint_text": "",
+                    "hidden_in_check_answers": true,
+                    "type": "radio",
+                    "answer_options": {
+                      "0": {
+                        "value": "Yes"
+                      },
+                      "1": {
+                        "value": "No"
+                      }
+                    }
+                  }
+                },
+                "derived": true,
+                "depends_on": [false]
               }
             }
           }

spec/models/form_spec.rb

@@ -190,5 +190,13 @@ RSpec.describe Form, type: :model do
         expect(form.invalidated_page_questions(case_log).map(&:id).uniq).to eq(expected_invalid)
       end
     end
+
+    context "when a page is marked as `derived`" do
+      let(:case_log) { FactoryBot.build(:case_log, :in_progress, startdate: Time.utc(2023, 2, 2, 10, 36, 49)) }
+
+      it "does not count it's questions as invalidated" do
+        expect(form.enabled_page_questions(case_log).map(&:id).uniq).to include("tshortfall_known")
+      end
+    end
   end
 end