Creates a nested example group named by the submitted attribute, and then generates an example using the submitted block.

  # This ...
  describe Array do
    its(:size) { should == 0 }
  end

  # ... generates the same runtime structure as this:
  describe Array do
    describe "size" do
      it "should == 0" do
        subject.size.should == 0
      end
    end
  end

The attribute can be a Symbol or a String. Given a String with dots, the result is as though you concatenated that String onto the subject in an expression.

  describe Person do
    subject do
      Person.new.tap do |person|
        person.phone_numbers << "555-1212"
      end
    end

    its("phone_numbers.first") { should == "555-1212" }
  end

When the subject is a Hash, you can refer to the Hash keys by specifying a Symbol or String in an array.

  describe "a configuration Hash" do
    subject do
      { :max_users => 3,
        'admin' => :all_permissions }
    end

    its([:max_users]) { should == 3 }
    its(['admin']) { should == :all_permissions }

    # You can still access to its regular methods this way:
    its(:keys) { should include(:max_users) }
    its(:count) { should == 2 }
  end

Defines an explicit subject for an example group which can then be the implicit receiver (through delegation) of calls to should.

Examples

  describe CheckingAccount, "with $50" do
    subject { CheckingAccount.new(:amount => 50, :currency => :USD) }
    it { should have_a_balance_of(50, :USD) }
    it { should_not be_overdrawn }
  end

See +ExampleMethods#should+ for more information about this approach.