すごいぞRSpec(attribute of subject即ちits編)

例のごとく既出だけど今回はattribute of subjectについて。rspec-core(2.5.1)/features/subject/attribute_of_subject.feature参考。「it { subject.first.size.should eq 2 }」とかするのやだよね。そんなときはitsを使えばステキになるよって話。

基本的にはシンボルか文字列で指定する

describe Array do
  context 'when first created' do
    its(:size) { should eq 0 }
    its('size') { should eq 0 }
  end
end

% rspec -cfs attribute_of_subject_spec_1.rb

Array
  when first created
    size
      should == 0
    size
      should == 0

文字列ならネストした属性も指定できる！

class Person
  attr_reader :phone_numbers
  def initialize
    @phone_numbers = []
  end
end

describe Person do
  context 'with one phone number (555-1212)' do
    subject do
      person = Person.new
      person.phone_numbers << '555-1212'
      person
    end

    its('phone_numbers.first') { should eq '555-1212' }
  end
end

% rspec -cfs attribute_of_subject_spec_2.rb

Person
  with one phone number (555-1212)
    phone_numbers.first
      should == 555-1212

Finished in 0.0017 seconds
1 example, 0 failures

subjectがハッシュなら配列にキーを一個だけ入れて値をテストできる！！

describe Hash do
  context 'with two items' do
    subject { {:one => 1, 'two' => 2} }

    its(:size) { should eq 2 }
    its([:one]) { should eq 1 }
    its(['two']) { should eq 2 }
  end
end

% rspec -cfs attribute_of_subject_spec_3.rb

Hash
  with two items
    size
      should == 2
    [:one]
      should == 1
    ["two"]
      should == 2

Finished in 0.00441 seconds
3 examples, 0 failures

まとめ

subjectとitsの組み合わせでテストはだいぶシンプルに書けそうですね！って、また順番間違ったな、まだsubjectの解説してないわー。

つづく