Added its(attribute) method for implicit subjects

[#883 state:resolved milestone:"Next Release"]

features/subject/implicit_subject.feature

@@ -29,3 +29,15 @@ Feature: implicit subject
       """
     When I run "spec nested_subject_spec.rb"
     Then the stdout should include "1 example, 0 failures"
+
+  Scenario: subject with getters
+    Given a file named "subject_with_getter_spec.rb" with:
+      """
+      describe Array do
+        describe "when first created" do
+          its(:length) { should == 0 }
+        end
+      end
+      """
+    When I run "spec subject_with_getter_spec.rb"
+    Then the stdout should include "1 example, 0 failures"

lib/spec/example/subject.rb

@@ -11,13 +11,21 @@ module ExampleGroupMethods
         #     subject { CheckingAccount.new(:amount => 50, :currency => :USD) }
         #     it { should have_a_balance_of(50, :USD) }
         #     it { should_not be_overdrawn }
+        #     its(:currency) { should == :USD }
         #   end
         #
         # See +ExampleMethods#should+ for more information about this approach.
         def subject(&block)
           block.nil? ?
             explicit_subject || implicit_subject : @explicit_subject_block = block
         end
+
+        def its(attribute, &block)
+          describe(attribute) do
+            define_method(:subject) { super().send(attribute) }
+            it(&block)
+          end
+        end
 
         attr_reader :explicit_subject_block # :nodoc: