diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index 8f6faeb53..843b72670 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -88,6 +88,8 @@ class ApplicationController < ActionController::Base
   end
 
   def rescue_exception(exception)
+    return if Danbooru.config.debug_mode
+
     case exception
     when ActionView::Template::Error
       rescue_exception(exception.cause)
diff --git a/config/danbooru_default_config.rb b/config/danbooru_default_config.rb
index 0bb6d3459..beed3096d 100644
--- a/config/danbooru_default_config.rb
+++ b/config/danbooru_default_config.rb
@@ -52,6 +52,15 @@ module Danbooru
       "_danbooru2_session"
     end
 
+    # Debug mode does some things to make testing easier. It disables parallel
+    # testing and it replaces Danbooru's custom exception page with the default
+    # Rails exception page. This is only useful during development and testing.
+    #
+    # Usage: `DANBOORU_DEBUG_MODE=true bin/rails test
+    def debug_mode
+      false
+    end
+
     def source_code_url
       "https://github.com/danbooru/danbooru"
     end
diff --git a/test/test_helper.rb b/test/test_helper.rb
index 0959a8ccd..1af778120 100644
--- a/test/test_helper.rb
+++ b/test/test_helper.rb
@@ -30,11 +30,13 @@ class ActiveSupport::TestCase
   mock_post_version_service!
   mock_pool_version_service!
 
-  parallelize
-  parallelize_setup do |worker|
-    Rails.application.load_seed
+  unless Danbooru.config.debug_mode
+    parallelize
+    parallelize_setup do |worker|
+      Rails.application.load_seed
 
-    SimpleCov.command_name "#{SimpleCov.command_name}-#{worker}"
+      SimpleCov.command_name "#{SimpleCov.command_name}-#{worker}"
+    end
   end
 
   parallelize_teardown do |worker|