Ticket #6611: assert_difference.patch

actionpack/test/controller/assert_difference_test.rb

@@ +1 @@
+require File.dirname(__FILE__) + '/../abstract_unit'
+require File.dirname(__FILE__) + '/fake_controllers'
+
+class AssertDifferenceTest < Test::Unit::TestCase
+  AssertionFailedError = Test::Unit::AssertionFailedError
+  
+  class Model
+    cattr_accessor :count
+    self.count = 4
+    
+    attr_accessor :name
+  end
+  
+  def setup
+    @model = Model.new
+  end
+  
+  def test_default_increment_cattr_by_one
+    assert_nothing_raised { assert_difference(Model, :count) { Model.count += 1 } }
+  end
+
+  def test_increment_cattr_by_one
+    assert_nothing_raised { assert_difference(Model, :count, 1) { Model.count += 1 } }
+  end
+
+  def test_decrement_cattr_by_one
+    assert_nothing_raised { assert_difference(Model, :count, -1) { Model.count -= 1 } }
+  end
+  
+  def test_increment_cattr_by_two
+    assert_nothing_raised { assert_difference(Model, :count, 2) { Model.count += 2 } }
+  end
+  
+  def test_nil_difference
+    assert_nothing_raised { assert_difference(Model, :count, nil) { Model.count += 2 } }
+  end
+  
+  def test_change_attr
+    assert_nothing_raised { assert_difference(@model, :name) { @model.name = 'changed' } }
+  end
+  
+  def test_no_difference_without_change
+    assert_nothing_raised { assert_no_difference(@model, :name) {  } }
+  end
+  
+  def test_fails_no_difference_with_change
+    assert_raises(AssertionFailedError) { assert_no_difference(@model, :name) { @model.name = 'changed' } }
+  end
+  
+  def test_fails_off_by_one
+    assert_raises(AssertionFailedError) { assert_difference(Model, :count, 1) { Model.count += 2 } }
+  end
+  
+  def test_fails_no_difference_off_by_one
+    assert_raises(AssertionFailedError) { assert_no_difference(Model, :count) { Model.count += 1 } }
+  end
+  
+  def test_multiple_objects
+    @model2 = Model.new
+    assert_nothing_raised { assert_difference([@model, @model2], :name) { @model.name = @model2.name = 'changed'} }
+  end
+
+  def test_no_difference_multiple_objects
+    @model2 = Model.new
+    assert_nothing_raised { assert_no_difference([@model, @model2], :name) { } }
+  end
+end

actionpack/lib/action_controller/assertions/model_assertions.rb

@@ -7 +7 @@
-          assert record.valid?, record.errors.full_messages.join("\n")
-        end
-      end
+      
+      # Asserts that the given block modifies the specified object or objects.  The default behavior
+      # is to test that the method called is different by 1 for Fixnums and not equal for any other class.
+      #
+      #   assert_difference Group, :count do
+      #     post :create, :group => { :name => 'monkeys' }
+      #   end
+      #
+      # You can also check that multiple objects have been modified
+      #
+      #   assert_difference [ User, Group ], :count do
+      #     post :create, :user => { :name => "Curious George" }, :group => { :name => 'monkeys' }
+      #   end
+      #
+      # To test blocks that modify the result by more than 1 you can pass a third parameter to indicate
+      # the difference.  If you don't care about the difference you can set the third parameter to nil 
+      # and it will simply assert that the value has changed.
+      #
+      # This implementation is based off of http://blog.caboo.se/articles/2006/06/13/a-better-assert_difference
+      def assert_difference(objects, method = nil, difference = 1)
+        objects = [objects].flatten
+        initial_values = objects.inject([]) { |sum,obj| sum << obj.send(method) }
+        yield
+        clean_backtrace do
+          objects.each_with_index do |obj,i|
+            if initial_values[i].is_a?(Fixnum) && !difference.nil?
+              assert_equal initial_values[i] + difference, obj.send(method), "#{obj}##{method}"
+            elsif difference == 0
+              assert_equal initial_values[i], obj.send(method), "#{obj}##{method}"
+            else
+              assert_not_equal initial_values[i], obj.send(method), "#{obj}##{method}"
+            end
+          end
+        end
+      end
+      
+      # Asserts that the given block does not modify the specified object
+      def assert_no_difference(object, method, &block)
+        assert_difference object, method, 0, &block
+      end
-    end
-  end
-end