diff --git a/activesupport/lib/active_support/test_case.rb b/activesupport/lib/active_support/test_case.rb
index ae6f00b8619049cba5753ebf7651c5562dfb14fa..d9a668c0ea02602a78723b40b17114ea476ffcfb 100644
--- a/activesupport/lib/active_support/test_case.rb
+++ b/activesupport/lib/active_support/test_case.rb
@@ -9,7 +9,6 @@
 require 'active_support/testing/constant_lookup'
 require 'active_support/testing/time_helpers'
 require 'active_support/testing/file_fixtures'
-require 'active_support/testing/composite_filter'
 require 'active_support/core_ext/kernel/reporting'
 
 module ActiveSupport
@@ -39,15 +38,6 @@ def test_order=(new_order)
       def test_order
         ActiveSupport.test_order ||= :random
       end
-
-      def run(reporter, options = {})
-        if options[:patterns] && options[:patterns].any? { |p| p =~ /:\d+/ }
-          options[:filter] = \
-            Testing::CompositeFilter.new(self, options[:filter], options[:patterns])
-        end
-
-        super
-      end
     end
 
     alias_method :method_name, :name
diff --git a/activesupport/lib/active_support/testing/composite_filter.rb b/activesupport/lib/active_support/testing/composite_filter.rb
deleted file mode 100644
index bde723e30b8f3048f38e32133fe0f80a0724feb9..0000000000000000000000000000000000000000
--- a/activesupport/lib/active_support/testing/composite_filter.rb
+++ /dev/null
@@ -1,54 +0,0 @@
-require 'method_source'
-
-module ActiveSupport
-  module Testing
-    class CompositeFilter # :nodoc:
-      def initialize(runnable, filter, patterns)
-        @runnable = runnable
-        @filters = [ derive_regexp(filter), *derive_line_filters(patterns) ].compact
-      end
-
-      def ===(method)
-        @filters.any? { |filter| filter === method }
-      end
-
-      private
-        def derive_regexp(filter)
-          filter =~ %r%/(.*)/% ? Regexp.new($1) : filter
-        end
-
-        def derive_line_filters(patterns)
-          patterns.map do |file_and_line|
-            file, line = file_and_line.split(':')
-            Filter.new(@runnable, file, line) if file
-          end
-        end
-
-        class Filter # :nodoc:
-          def initialize(runnable, file, line)
-            @runnable, @file = runnable, File.expand_path(file)
-            @line = line.to_i if line
-          end
-
-          def ===(method)
-            return unless @runnable.method_defined?(method)
-
-            if @line
-              test_file, test_range = definition_for(@runnable.instance_method(method))
-              test_file == @file && test_range.include?(@line)
-            else
-              @runnable.instance_method(method).source_location.first == @file
-            end
-          end
-
-          private
-            def definition_for(method)
-              file, start_line = method.source_location
-              end_line = method.source.count("\n") + start_line - 1
-
-              return file, start_line..end_line
-            end
-        end
-    end
-  end
-end
diff --git a/railties/lib/rails/test_unit/line_filtering.rb b/railties/lib/rails/test_unit/line_filtering.rb
new file mode 100644
index 0000000000000000000000000000000000000000..65f76f21a6e11201eed144d43e800e5dd9ba50a3
--- /dev/null
+++ b/railties/lib/rails/test_unit/line_filtering.rb
@@ -0,0 +1,63 @@
+require 'method_source'
+
+module Rails
+  module LineFiltering # :nodoc:
+    def run(reporter, options = {})
+      if options[:patterns] && options[:patterns].any? { |p| p =~ /:\d+/ }
+        options[:filter] = \
+          CompositeFilter.new(self, options[:filter], options[:patterns])
+      end
+
+      super
+    end
+  end
+
+  class CompositeFilter # :nodoc:
+    def initialize(runnable, filter, patterns)
+      @runnable = runnable
+      @filters = [ derive_regexp(filter), *derive_line_filters(patterns) ].compact
+    end
+
+    def ===(method)
+      @filters.any? { |filter| filter === method }
+    end
+
+    private
+      def derive_regexp(filter)
+        filter =~ %r%/(.*)/% ? Regexp.new($1) : filter
+      end
+
+      def derive_line_filters(patterns)
+        patterns.map do |file_and_line|
+          file, line = file_and_line.split(':')
+          Filter.new(@runnable, file, line) if file
+        end
+      end
+  end
+
+  class Filter # :nodoc:
+    def initialize(runnable, file, line)
+      @runnable, @file = runnable, File.expand_path(file)
+      @line = line.to_i if line
+    end
+
+    def ===(method)
+      return unless @runnable.method_defined?(method)
+
+      if @line
+        test_file, test_range = definition_for(@runnable.instance_method(method))
+        test_file == @file && test_range.include?(@line)
+      else
+        @runnable.instance_method(method).source_location.first == @file
+      end
+    end
+
+    private
+      def definition_for(method)
+        file, start_line = method.source_location
+        end_line = method.source.count("\n") + start_line - 1
+
+        return file, start_line..end_line
+      end
+  end
+end
diff --git a/railties/lib/rails/test_unit/railtie.rb b/railties/lib/rails/test_unit/railtie.rb
index 75180ff97829951e5d82a507c06543919b62b770..511cee33bd6341d05a276b81e90a738a20d3cb2f 100644
--- a/railties/lib/rails/test_unit/railtie.rb
+++ b/railties/lib/rails/test_unit/railtie.rb
@@ -1,3 +1,5 @@
+require 'rails/test_unit/line_filtering'
+
 if defined?(Rake.application) && Rake.application.top_level_tasks.grep(/^(default$|test(:|$))/).any?
   ENV['RAILS_ENV'] ||= 'test'
 end
@@ -11,6 +13,10 @@ class TestUnitRailtie < Rails::Railtie
       c.integration_tool :test_unit
     end
 
+    initializer "test_unit.line_filtering" do
+      ActiveSupport::TestCase.extend Rails::LineFiltering
+    end
+
     rake_tasks do
       load "rails/test_unit/testing.rake"
     end