「簡単なものこそBDDで！」 〜 LTSpiral #2 で発表してきました。

先週、関西IT系若手勉強会 LTSpiral (
LTSpiral | Google グループ
) 第二回に参加してきました。1回目は社会人3年目まで(学生含む)が対象でしたが、今回は社会人6年目までに拡大され、パワーアップ！（？） IT系といっても業界はWebからインフラ、組込み（僕だけ？）まで、立場もエンジニアだけではないし、いろんな人が集まってわいわい話ができるのが面白いです。

僕も2枠(20分)いただいて、「BDDやろうぜ！」とお話してきました。

簡単なものこそBDDで！

View more presentations from Ryo Nagai.

使ったソースコードはこちら。とりあえず完成形の sample3 だけ載せておきます。

sample3_spec.rb (スペックのほう)

# -*- encoding: utf-8 -*-

require 'sample3'

describe Animal do
    describe '#new' do
        it "should not be raised" do
            lambda{ Animal.new }.should raise_error
        end
    end
end

describe Bear do
    before :each do
        @janos = Bear.new("Janos")
    end

    describe '#name' do
        it "should return its name" do
            @janos.name.should == "Janos"
        end
    end

    describe '#kind' do
        it "should return its kind" do
            @janos.kind.should == "bear"
        end
    end
end

describe Penguin do
    before :each do
        @penguin = Penguin.new("Brik")
    end

    describe '#name' do
        it "should return its name" do
            @penguin.name.should == "Brik"
        end
    end

    describe '#kind' do
        it "should return its kind" do
            @penguin.kind.should == "penguin"
        end
    end
end


describe Cage do
    before :each do
        @cage = Cage.new("New Cage")

        @penguin1 = Penguin.new("Penpen")
        @penguin2 = Penguin.new("Liebe")
        @bear1 = Bear.new("Wink")
        @bear2 = Bear.new("White")

        @cage.add_member(@penguin1)
        @cage.add_member(@bear1)

        @empty_cage = Cage.new("Empty Cage")
    end

    describe '#new' do
        it "should create an empty cage with given name" do
            newcage = Cage.new("Green Yard")
            newcage.name.should == "Green Yard"
            newcage.members.should be_empty
        end

        it "should give default name if no name was given" do
            newcage = Cage.new
            newcage.name.should == "No Name"
        end
    end

    describe '#name' do
        it "should return its name" do
            @cage.name.should == "New Cage"
        end
    end

    describe '#add_member(animal)' do
        it "should add the animal into the cage" do
            @cage.add_member(@bear2)
            @cage.should have_a(@bear2)
        end

        it "should not accept non-animal" do
            lambda{ @cage.add_member(123) }.should raise_error
        end
    end

    describe '#members' do
        it "should return the list of members" do
            @cage.members.should have(2).items
            @empty_cage.members.should be_empty
        end
    end

    describe '#num_of_members' do
        it "should return the number of members" do
            @cage.num_of_members.should == 2
            @empty_cage.num_of_members.should == 0
        end
    end

    describe '#introduce_by_name' do
        it "should call all names" do
            @cage.introduce_by_name.should include("Penpen")
            @cage.introduce_by_name.should include("Wink")
        end

        it "should tell it if there is no animals" do
            @empty_cage.introduce_by_name.should == "There is no animal"
        end
    end

    describe '#introduce_by_kind' do
        it "should classify animals and count" do
            @cage.add_member(@bear2)
            @cage.introduce_by_kind.should include("1 penguin")
            @cage.introduce_by_kind.should include("2 bears")
        end

        it "should tell it if there is no animals" do
            @empty_cage.introduce_by_kind.should == "There is no animal"
        end
    end
end

sample3.rb (こっちが本体)

# -*- encoding: utf-8 -*-

class Animal
    def initialize(name)
        raise "Animal cannot be used without inherit"
    end

    attr_reader :name
end

class Bear < Animal
    def initialize(name)
        @name = name
    end
    
    def kind
        "bear"
    end
end

class Penguin < Animal
    def initialize(name)
        @name = name
    end

    def kind
        "penguin"
    end
end


class Cage
    def initialize(name="No Name")
        @name = name
        @members = []
    end

    attr_reader :name, :members

    def add_member(animal)
        if animal.is_a? Animal
            @members << animal
        else
            raise "#{animal} is not an animal"
        end
    end

    def has_a?(animal)
        members.include?(animal)
    end

    def num_of_members
        members.size
    end

    def introduce_by_name
        return "There is no animal" if num_of_members == 0

        "There are " + members.map{|x| x.name}.join(", ")
    end

    def introduce_by_kind
        return "There is no animal" if num_of_members == 0

        # classify by kind
        count_hash = Hash.new(0)
        members.each do |x|
            count_hash[x.kind] += 1
        end

        ary = []
        count_hash.each do |kind, num|
            ary << "#{num} #{kind}s" # now use plural if one
        end

        "There are " + ary.join(", ")
    end
end