ExampleGroup .its() creates new Example with a subject modifier

example_specs/passing/subject_example.rb

@@ -0,0 +1,45 @@
+require File.dirname(__FILE__) + '/spec_helper'
+
+module SubjectExample
+  class OneThing
+    attr_accessor :what_things_do
+    def initialize
+      self.what_things_do = "stuff"
+    end
+  end
+
+  # implicit subject
+  describe OneThing do
+    it "should do what things do" do
+      subject.what_things_do.should == "stuff"
+    end
+    it "should be a OneThing" do
+      should == subject
+    end
+    its(:what_things_do) { should == "stuff" }
+  end
+
+  # explicit subject
+  describe SubjectExample::OneThing do
+    subject { SubjectExample::OneThing.new }
+    it "should do what things do" do
+      subject.what_things_do.should == "stuff"
+    end
+    it "should be a OneThing" do
+      should == subject
+    end
+    its(:what_things_do) { should == "stuff" }
+  end
+
+  # modified subject
+  describe OneThing do
+    subject { SubjectExample::OneThing.new }
+    before { subject.what_things_do = "more stuff" }
+    it "should do what things do" do
+      subject.what_things_do.should == "more stuff"
+    end
+    its(:what_things_do) { should == "more stuff" }
+  end
+
+end
+

lib/rspec/core/example.rb

@@ -35,6 +35,10 @@ def inspect
         @metadata[:full_description]
       end
 
+      def subject_modifier
+        @metadata[:subject_modifier]
+      end
+
       def to_s
         inspect
       end

lib/rspec/core/example_group.rb

@@ -28,6 +28,13 @@ def self.#{name}(desc=nil, options={}, &block)
         END_RUBY
       end
 
+      def self.its(modifier, desc=nil, options={}, &block)
+        options.update(:pending => true) unless block
+        options.update(:caller => caller)
+        options.update(:subject_modifier => modifier)
+        examples << Rspec::Core::Example.new(self, desc, options, block)
+      end
+
       define_example_method :example
 
       class << self

lib/rspec/core/subject.rb

@@ -1,17 +1,17 @@
 module Rspec
   module Core
     module Subject
-      
+
       def self.included(kls)
         kls.extend   ClassMethods
         kls.__send__ :alias_method, :__should_for_example_group__,     :should
         kls.__send__ :alias_method, :__should_not_for_example_group__, :should_not
       end
-      
+
       def subject
-        @subject ||= instance_eval(&self.class.subject)
+        modify_subject? ? modified_subject : unmodified_subject
       end
-      
+
       # When +should+ is called with no explicit receiver, the call is
       # delegated to the object returned by +subject+. Combined with
       # an implicit subject (see +subject+), this supports very concise
@@ -37,7 +37,7 @@ def should(matcher=nil, message=nil)
       def should_not(matcher=nil, message=nil)
         self == subject ? self.__should_not_for_example_group__(matcher) : subject.should_not(matcher,message)
       end
-      
+
       module ClassMethods
         # Defines an explicit subject for an example group which can then be the
         # implicit receiver (through delegation) of calls to +should+.
@@ -54,7 +54,7 @@ module ClassMethods
         def subject(&block)
           block ? @explicit_subject_block = block : explicit_subject || implicit_subject
         end
-      
+
         attr_reader :explicit_subject_block # :nodoc:
 
       private
@@ -72,6 +72,23 @@ def implicit_subject
           Class === described ? lambda { described.new } : lambda { described }
         end
       end
+
+    private
+
+      def modify_subject?
+        !running_example.nil? &&
+        !running_example.subject_modifier.nil? &&
+        running_example.state == :block
+      end
+
+      def unmodified_subject
+        @unmodified_subject ||= instance_eval(&self.class.subject)
+      end
+
+      def modified_subject
+        unmodified_subject.send(running_example.subject_modifier)
+      end
+
     end
   end
 end

spec/rspec/core/example_group_spec.rb

@@ -168,6 +168,12 @@ module Rspec::Core
         group.examples.size.should == 1
       end
 
+      it "should allow adding an example using 'its'" do
+        group = ExampleGroup.create
+        group.its(:some_method) { }
+        group.examples.size.should == 1
+      end
+
       it "should expose all examples at examples" do
         group = ExampleGroup.create
         group.it("should do something 1") { }
@@ -374,6 +380,26 @@ def self.count
         SelfObserver.cache.length.should == 1
       end
     end
+
+    describe "example added with its" do
+      it "should have a subject_modifier" do
+        group    = ExampleGroup.create
+        examples = group.its(:some_method) { }
+        example  = examples.last
+        example.subject_modifier.should === :some_method
+      end
+    end
+
+    describe "#its" do
+      its(:class, "should be ExampleGroup") { should == Rspec::Core::ExampleGroup }
+      it "does not interfere between tests" do
+        subject.class.should == Rspec::Core::ExampleGroup
+      end
+      context "subject modified in before block" do
+        before { subject.class.should == Rspec::Core::ExampleGroup }
+        its(:class, "should be ExampleGroup") { should == Rspec::Core::ExampleGroup }
+      end
+    end
   end
 
 end

spec/rspec/core/example_spec.rb

@@ -29,6 +29,10 @@
       @example.should respond_to(:example_block)
     end
 
+    it "should have one for its subject modifier" do
+      @example.should respond_to(:subject_modifier)
+    end
+
     it "should have one for its state" do
       @example.should respond_to(:state)
     end