5 files changed, 68 insertions, 0 deletions
diff --git a/activesupport/CHANGELOG b/activesupport/CHANGELOG
index f8ac504127..28ff1136e2 100644
--- a/activesupport/CHANGELOG
+++ b/activesupport/CHANGELOG
@@ -1,5 +1,7 @@
 *SVN*
 
+* Added assert_difference and assert_no_difference to test/unit assertions [Tobias Luetke]
+
 * Removed breakpointer and Binding.of_caller in favor of relying on ruby-debug by Kent Sibilev since the breakpointer has been broken since Ruby 1.8.4 and will not be coming back [DHH]
 
 * Added parsing of file type in Hash.xml_in so you can easily do file uploads with base64 from an API [DHH]
diff --git a/activesupport/lib/active_support.rb b/activesupport/lib/active_support.rb
index e094cbe0fe..668bb6e228 100644
--- a/activesupport/lib/active_support.rb
+++ b/activesupport/lib/active_support.rb
@@ -43,3 +43,4 @@ require 'active_support/duration'
 require 'active_support/json'
 
 require 'active_support/multibyte'
+
diff --git a/activesupport/lib/active_support/core_ext/test.rb b/activesupport/lib/active_support/core_ext/test.rb
new file mode 100644
index 0000000000..193599b8dc
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/test.rb
@@ -0,0 +1,2 @@
+require File.dirname(__FILE__) + '/test/difference'
+
diff --git a/activesupport/lib/active_support/core_ext/test/difference.rb b/activesupport/lib/active_support/core_ext/test/difference.rb
new file mode 100644
index 0000000000..1f85f0f4b7
--- /dev/null
+++ b/activesupport/lib/active_support/core_ext/test/difference.rb
@@ -0,0 +1,29 @@
+
+module Test #:nodoc:
+  module Unit #:nodoc:
+    class TestCase #:nodoc:
+      
+      # Test difference between the return value of method on object for duration of the block
+      def assert_difference(objects, method = nil, difference = 1)
+        objects = [objects].flatten
+        initial_values = objects.inject([]) { |sum,obj| sum << obj.send(method) }
+        yield
+        if difference.nil?
+          objects.each_with_index { |obj,i|
+            assert_not_equal initial_values[i], obj.send(method), "#{obj}##{method}"
+          }
+        else
+          objects.each_with_index { |obj,i|
+            assert_equal initial_values[i] + difference, obj.send(method), "#{obj}##{method}"
+          }
+        end
+      end
+
+      # Test absence of difference between the return value of method on object for duration of the block
+      def assert_no_difference(objects, method = nil, &block)
+        assert_difference objects, method, 0, &block
+      end
+
+    end
+  end
+end
diff --git a/activesupport/test/test_test.rb b/activesupport/test/test_test.rb
new file mode 100644
index 0000000000..63a44e9379
--- /dev/null
+++ b/activesupport/test/test_test.rb
@@ -0,0 +1,34 @@
+require File.dirname(__FILE__) + '/abstract_unit'
+
+class AssertDifferenceTest < Test::Unit::TestCase
+  
+  def setup
+    @object = Class.new { attr_accessor :num }.new    
+  end
+  
+  def test_assert_no_difference
+    @object.num = 0
+    
+    assert_no_difference @object, :num do
+      # ...
+    end
+      
+  end
+  def test_assert_difference
+    @object.num = 0
+    
+    
+    assert_difference @object, :num, +1 do
+      @object.num = 1
+    end
+      
+  end
+
+  def test_methods_available
+    
+    assert self.respond_to?(:assert_difference)
+    assert self.respond_to?(:assert_no_difference)
+    
+  end
+
+end