DEV: Support for running theme test with Ember CLI (second attempt)

This PR includes support for running theme tests in legacy ember
production envrionments.

app/helpers/application_helper.rb

@@ -13,9 +13,11 @@ module ApplicationHelper
     @extra_body_classes ||= Set.new
   end
 
-  def discourse_config_environment
+  def discourse_config_environment(testing: false)
+
     # TODO: Can this come from Ember CLI somehow?
-    { modulePrefix: "discourse",
+    config = {
+      modulePrefix: "discourse",
       environment: Rails.env,
       rootURL: Discourse.base_path,
       locationType: "auto",
@@ -32,7 +34,16 @@ module ApplicationHelper
         version: "#{Discourse::VERSION::STRING} #{Discourse.git_version}",
         exportApplicationGlobal: true
       }
-    }.to_json
+    }
+
+    if testing
+      config[:environment] = "test"
+      config[:locationType] = "none"
+      config[:APP][:autoboot] = false
+      config[:APP][:rootElement] = '#ember-testing'
+    end
+
+    config.to_json
   end
 
   def google_universal_analytics_json(ua_domain_name = nil)

app/helpers/qunit_helper.rb

@@ -1,6 +1,38 @@
 # frozen_string_literal: true
 
 module QunitHelper
+
+  def vendor_theme_tests
+    return preload_script("vendor-theme-tests") if @legacy_ember
+    preload_script("vendor")
+  end
+
+  def support_bundles
+    result = []
+    if Rails.env.production? || @legacy_ember
+      result << preload_script("discourse/tests/test-support-rails")
+      result << preload_script("discourse/tests/test-helpers-rails")
+    else
+      result << preload_script("test-support")
+      result << preload_script("test-helpers")
+    end
+    result.join("\n").html_safe
+  end
+
+  def boot_bundles
+    result = []
+    if @legacy_ember
+      result << preload_script("discourse/tests/test_starter")
+    elsif @is_proxied
+      result << preload_script("scripts/discourse-test-listen-boot")
+      result << preload_script("scripts/discourse-boot")
+    else
+      result << preload_script("discourse-test-listen-boot")
+      result << preload_script("discourse-boot")
+    end
+    result.join("\n").html_safe
+  end
+
   def theme_tests
     theme = Theme.find_by(id: request.env[:resolved_theme_id])
     return "" if theme.blank?