1 files changed, 5 insertions, 3 deletions
diff --git a/railties/lib/rails/test_unit/railtie.rb b/railties/lib/rails/test_unit/railtie.rb
index 511cee33bd..746120e6a1 100644
--- a/railties/lib/rails/test_unit/railtie.rb
+++ b/railties/lib/rails/test_unit/railtie.rb
@@ -1,7 +1,7 @@
-require 'rails/test_unit/line_filtering'
+require "rails/test_unit/line_filtering"
 
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
-  ENV['RAILS_ENV'] ||= 'test'
+  ENV["RAILS_ENV"] ||= "test"
 end
 
 module Rails
@@ -14,7 +14,9 @@ module Rails
     end
 
     initializer "test_unit.line_filtering" do
-      ActiveSupport::TestCase.extend Rails::LineFiltering
+      ActiveSupport.on_load(:active_support_test_case) {
+        ActiveSupport::TestCase.extend Rails::LineFiltering
+      }
     end
 
     rake_tasks do