feat: add depends on behaviour

app/models/form/sales/pages/mortgage_length.rb

@@ -1,4 +1,11 @@
 class Form::Sales::Pages::MortgageLength < ::Form::Page
+  def initialize(id, hsh, subsection)
+    super
+    @depends_on = [{
+                     "mortgageused" => 1,
+                   }]
+  end
+
   def questions
     @questions ||= [
       Form::Sales::Questions::MortgageLength.new(nil, nil, self),

spec/models/form/sales/pages/mortgage_length_spec.rb

@@ -28,6 +28,8 @@ RSpec.describe Form::Sales::Pages::MortgageLength, type: :model do
   end
 
   it "has correct depends_on" do
-    expect(page.depends_on).to be_nil
+    expect(page.depends_on).to eq([{
+      "mortgageused" => 1,
+    }])
   end
 end