triangle.rb

class Triangle
  def initialize(sides)
    @sides = sides
  end

  def type
    @sides.sort!
    if @sides[0] + @sides[1] <= @sides[2]
      :invalid
    else
      case @sides.uniq.length
      when 1
        :equilateral
      when 2
        :isosceles
      when 3
        :scalene
      end
    end
  end
end


require 'rspec'

describe Triangle do
  it 'is initialized with three sides as arguments' do
    Triangle.new([1,2,3]).should be_an_instance_of Triangle
  end

  it 'is equilateral if all three sides are equal' do
    triangle = Triangle.new([1,1,1])
    triangle.type.should eq :equilateral
  end

  it 'is isosceles if only two sides are equal' do
    triangle = Triangle.new([2,2,3])
    triangle.type.should eq :isosceles
  end

  it 'is scalene if no sides are equal' do
    triangle = Triangle.new([2,4,3])
    triangle.type.should eq :scalene
  end

  it 'is invalid if one side is at least as long as the other two combined' do
    triangle = Triangle.new([1,2,3])
    triangle.type.should eq :invalid
  end
end