From 689b529ea82b2375ee3f743eb82da9b83e0d00ff Mon Sep 17 00:00:00 2001
From: Marcel Molina <marcel@vernix.org>
Date: Tue, 8 May 2007 03:54:34 +0000
Subject: Simplify API of assert_difference by passing in an expression that is
 evaluated before and after the passed in block. See documenation for examples
 of new API. [Marcel Molina Jr.]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@6693 5ecf4fe2-1ee6-0310-87b1-e25e094e27de
---
 .../lib/active_support/core_ext/test/difference.rb | 51 +++++++++++++---------
 1 file changed, 31 insertions(+), 20 deletions(-)

(limited to 'activesupport/lib/active_support/core_ext/test')

diff --git a/activesupport/lib/active_support/core_ext/test/difference.rb b/activesupport/lib/active_support/core_ext/test/difference.rb
index 1f85f0f4b7..65dae3469b 100644
--- a/activesupport/lib/active_support/core_ext/test/difference.rb
+++ b/activesupport/lib/active_support/core_ext/test/difference.rb
@@ -1,29 +1,40 @@
-
 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) }
+    class TestCase #:nodoc:      
+      # Test numeric difference between the return value of an expression as a result of what is evaluated
+      # in the yielded block.
+      #
+      #   assert_difference 'Post.count' do
+      #     post :create, :post => {...}
+      #   end
+      #
+      # An arbitrary expression is passed in an evaluated.
+      #
+      #   assert_difference 'assigns(:post).comments(:reload).size' do
+      #     post :create, :comment => {...}
+      #   end
+      #
+      # An arbitrary positive or negative difference can be specified. The default is 1.
+      #
+      #   assert_difference 'Post.count', -1 do
+      #     post :delete, :id => ...
+      #   end
+      def assert_difference(expression, difference = 1, &block)
+        expression_evaluation = lambda { eval(expression) }
+        original_value        = expression_evaluation.call
         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
+        assert_equal original_value + difference, expression_evaluation.call
       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
+      # Assertion that the numeric result of evaluating an expression is not changed before and after
+      # invoking the passed in block.
+      #
+      #   assert_no_difference 'Post.count' do
+      #     post :create, :post => invalid_attributes
+      #   end
+      def assert_no_difference(expression, &block)
+        assert_difference expression, 0, &block
       end
-
     end
   end
 end
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