framework_test.rb also dependent on RAILS_ENV=development

railties/test/application/initializers/frameworks_test.rb

@@ -5,11 +5,17 @@ module ApplicationTests
     include ActiveSupport::Testing::Isolation
 
     def setup
+      @prev_rails_env = ENV['RAILS_ENV']
+      ENV['RAILS_ENV'] = 'development'
       build_app
       boot_rails
       FileUtils.rm_rf "#{app_path}/config/environments"
     end
 
+    def teardown
+      ENV['RAILS_ENV'] = @prev_rails_env
+    end
+
     # AC & AM
     test "set load paths set only if action controller or action mailer are in use" do
       assert_nothing_raised NameError do