Module: Its::ExampleGroupMethods

Defined in:
lib/its.rb

Instance Method Summary collapse

Instance Method Details

#its(attribute, *args, &block) ⇒ Object

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 eq(0) }
end

# ... generates the same runtime structure as this:
describe Array do
  describe "size" do
    it "should eq(0)" do
      subject.size.should eq(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 eq("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 eq(3) }
  its(['admin']) { should eq(:all_permissions) }

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

You can also pass any additional arguments the target method can accept:

describe Person do
  subject do
    Person.new.tap do |person|
      person.phone_numbers << "123-123"
      person.phone_numbers << "234-234"
      person.phone_numbers << "xxx-xxx"
    end
  end

  its("phone_numbers.first", 2) { should == ["123-123", "234-234"]
end

This is the extraction from the RSpec Core. For reference, see:

This modifies the following behaviour:

  • calls the target with arguments passed it

  • changes the description to include the args (if any)



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# File 'lib/its.rb', line 76

def its(attribute, *args, &block)
  desc = attribute.to_s
  desc += "(#{args.map{|a| a.nil? ? 'nil' : a.to_s}.join(', ')})" unless args.empty?

  describe(desc) do
    example do
      self.class.class_eval do
        define_method(:subject) do
          @_subject ||= if attribute.is_a?(Array)
                          super()[*attribute]
                        else
                          attribute.to_s.split('.').inject(super()) do |target, method|
                            target.send(method, *args)
                          end
                        end
        end
      end
      instance_eval(&block)
    end
  end
end