rpg_battle.rb

module RPG
  class Battle

    ARENAS = [:town, :desert, :jungle, :mountain, :boat]

    attr_accessor :fighters
    attr_reader :battleground

    def initialize(fighter_a, fighter_b)
      @fighters = [fighter_a, fighter_b]
      @battleground = ARENAS.sort_by { rand }.first
    end

    def first_attacker
      fighters.sort do |b, a|
        a.initiative_roll <=> b.initiative_roll
      end.first
    end
  end

  class Fighter
    attr_accessor :name, :hp, :strength, :defense

    def initialize(*options)
      options = Hash[*options]
      @name = options[:name]
      @hp = options[:hp]
      @strength = options[:strength]
      @defense = options[:defense]
    end

    def initiative_roll
      @hp + @strength + @defense
    end

    def defend_from(attacker)
      attacker.defense < defense
    end

    def attack(opponent, amount)
      opponent.hit_for!(amount)
    end

    def hit_for!(amount)
      @hp -= amount
    end

    def heal_for!(amount)
      @hp += amount
    end

    def alive?
      @hp > 0
    end
  end
end

spec.rb

require_relative 'spec_helper'
require_relative 'rpg_battle'

module RPG
  describe Battle do
    it "enters battle with 2 opponents" do
      battle = Battle.new(mock, mock)
      battle.fighters.size.should == 2
    end

    it "chooses a battle ground" do
      battle = Battle.new(mock, mock)
      battle.battleground.should_not be_nil
    end

    it "chooses a valid battle ground" do
      battle = Battle.new(mock, mock)
      RPG::Battle::ARENAS.should include battle.battleground
    end

    it "chooses a first attacker based on their initiative roll" do
      fighter1 = mock(initiative_roll: 10)
      fighter2 = mock(initiative_roll: 20)

      battle = Battle.new(fighter1, fighter2)
      battle.first_attacker.should == fighter2
    end
  end

  describe Fighter do
    it "calculates an initiative roll based on their attributes" do
      fighter = Fighter.new(hp: 10, strength: 10, defense: 10)
      fighter.initiative_roll.should == 30
    end

    it "can defend from an attack" do
      fighter = Fighter.new(defense: 10)
      fighter.defend_from(mock(defense: 5)).should == true
    end

    it "can fail to defend from an attack" do
      fighter = Fighter.new(defense: 5)
      fighter.defend_from(mock(defense: 10)).should == false
    end

    it "can attack an opponent" do
      opponent = mock
      opponent.should_receive(:hit_for!).with(10)

      fighter = Fighter.new
      fighter.attack(opponent, 10)
    end

    it "can take damage" do
      fighter = Fighter.new(hp: 10)
      fighter.hit_for!(10)
      fighter.hp.should == 0
    end

    it "can heal" do
      fighter = Fighter.new(hp: 10)
      fighter.heal_for!(10)
      fighter.hp.should == 20
    end

    it "knows if he is alive" do
      fighter = Fighter.new(hp: 10)
      fighter.alive?.should == true
    end

    it "knows if he is dead" do
      fighter = Fighter.new(hp: 0)
      fighter.alive?.should == false
    end
  end
end