1 files changed, 11 insertions, 7 deletions
diff --git a/activesupport/lib/active_support/testing/assertions.rb b/activesupport/lib/active_support/testing/assertions.rb
index ce2f44efd6..ca51adba1e 100644
--- a/activesupport/lib/active_support/testing/assertions.rb
+++ b/activesupport/lib/active_support/testing/assertions.rb
@@ -31,13 +31,17 @@ module ActiveSupport
       #   assert_difference 'Article.count', -1, "An Article should be destroyed" do
       #     post :delete, :id => ...
       #   end
-      def assert_difference(expressions, difference = 1, message = nil, &block)
-        expression_evaluations = Array(expressions).collect{ |expression| lambda { eval(expression, block.send(:binding)) } }
+      def assert_difference(expression, difference = 1, message = nil, &block)
+        b = block.send(:binding)
+        exps = Array.wrap(expression)
+        before = exps.map { |e| eval(e, b) }
 
-        original_values = expression_evaluations.inject([]) { |memo, expression| memo << expression.call }
         yield
-        expression_evaluations.each_with_index do |expression, i|
-          assert_equal original_values[i] + difference, expression.call, message
+
+        exps.each_with_index do |e, i|
+          error = "#{e.inspect} didn't change by #{difference}"
+          error = "#{message}.\n#{error}" if message
+          assert_equal(before[i] + difference, eval(e, b), error)
         end
       end
 
@@ -53,8 +57,8 @@ module ActiveSupport
       #   assert_no_difference 'Article.count', "An Article should not be destroyed" do
       #     post :create, :article => invalid_attributes
       #   end
-      def assert_no_difference(expressions, message = nil, &block)
-        assert_difference expressions, 0, message, &block
+      def assert_no_difference(expression, message = nil, &block)
+        assert_difference expression, 0, message, &block
       end
     end
   end