Use lockstep to remove test flakiness

Gemfile

@@ -13,8 +13,6 @@ gem "pg", "~> 1.1"
 gem "puma", "~> 5.0"
 # Transpile app-like JavaScript. Read more: https://github.com/rails/webpacker
 gem "webpacker", "~> 5.0"
-# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
-gem "jbuilder", "~> 2.7"
 # Reduces boot times through caching; required in config/boot.rb
 gem "bootsnap", ">= 1.4.4", require: false
 # Gov.UK frontend components
@@ -61,6 +59,7 @@ end
 
 group :test do
   gem "capybara", require: false
+  gem "capybara-lockstep"
   gem "factory_bot_rails"
   gem "selenium-webdriver", require: false
   gem "simplecov", require: false

Gemfile.lock

@@ -137,6 +137,11 @@ GEM
       rack-test (>= 0.6.3)
       regexp_parser (>= 1.5, < 3.0)
       xpath (~> 3.2)
+    capybara-lockstep (1.1.0)
+      activesupport (>= 3.2)
+      capybara (>= 2.0)
+      ruby2_keywords
+      selenium-webdriver (>= 3)
     chartkick (4.1.2)
     childprocess (4.1.0)
     coderay (1.1.3)
@@ -193,8 +198,6 @@ GEM
       railties (>= 5.2, < 6.2)
       responders (>= 2, < 4)
     iniparse (1.5.0)
-    jbuilder (2.11.3)
-      activesupport (>= 5.0.0)
     jquery-rails (4.4.0)
       rails-dom-testing (>= 1, < 3)
       railties (>= 4.2.0)
@@ -399,6 +402,7 @@ DEPENDENCIES
   bootsnap (>= 1.4.4)
   byebug
   capybara
+  capybara-lockstep
   chartkick
   devise
   discard
@@ -407,7 +411,6 @@ DEPENDENCIES
   govuk-components
   govuk_design_system_formbuilder
   hotwire-rails
-  jbuilder (~> 2.7)
   json-schema
   listen (~> 3.3)
   overcommit (>= 0.37.0)

app/views/layouts/application.html.erb

@@ -15,6 +15,7 @@
     <%= favicon_link_tag asset_pack_path('media/images/govuk-apple-touch-icon-180x180.png'), rel: 'apple-touch-icon', type: 'image/png', size: '180x180' %>
     <%= stylesheet_pack_tag 'application', media: 'all' %>
     <%= javascript_pack_tag 'application', defer: true %>
+    <%= capybara_lockstep if defined?(Capybara::Lockstep) %>
 
     <p class="notice"><%= notice %></p>
     <p class="alert"><%= alert %></p>