Triangle.rb

class TriangleError < Exception
end

class Triangle
  attr_accessor :side1, :side2, :side3

  def initialize(side1, side2, side3)
    @side1 = side1
    @side2 = side2
    @side3 = side3
    self.validate
  end

  def validate
    raise TriangleError if side1 <= 0 && side2 <= 0 && side3 <= 0
    raise TriangleError if side1 + side2 <= side3 ||
    side1 + side3 <= side2 || side2 + side3 <= side1
  end

  def kind
    if side1 == side2 && side2 == side3
      :equilateral
    elsif side1 == side2 || side2 == side3 || side1 == side3
      :isosceles
    else
      :scalene
    end     
  end

end
 
RSpec.configure do |config|
  # Use color in STDOUT
  config.color_enabled = true
 
  # Use color not only in STDOUT but also in pagers and files
  config.tty = true
 
  # Use the specified formatter
  config.formatter = :progress # :progress, :html, :textmate
end
 
describe 'Triangle' do
 
  it 'knows that equilateral triangles have equal sides' do
    Triangle.new(2, 2, 2).kind.should eq(:equilateral)
  end
 
  it 'knows that larger equilateral triangles also have equal sides' do
    Triangle.new(10, 10, 10).kind.should eq(:equilateral)
  end
 
  it 'knows that isosceles triangles have last two sides equal' do
    Triangle.new(3, 4, 4).kind.should eq(:isosceles)
  end
 
  it 'knows that isosceles triangles have first and last sides equal' do
    Triangle.new(4, 3, 4).kind.should eq(:isosceles)
  end
 
  it 'knows that isosceles triangles have two first sides equal' do
    Triangle.new(4, 4, 3).kind.should eq(:isosceles)
  end
 
  it 'knows that isosceles triangles have in fact exactly two sides equal' do
    Triangle.new(10, 10, 2).kind.should eq(:isosceles)
  end
 
  it 'knows that scalene triangles have no equal sides' do
    Triangle.new(3, 4, 5).kind.should eq(:scalene)
  end
 
  it 'knows that scalene triangles have no equal sides at a larger scale too' do
    Triangle.new(10, 11, 12).kind.should eq(:scalene)
  end
 
  it 'knows that scalene triangles have no equal sides in descending order either' do
    Triangle.new(5, 4, 2).kind.should eq(:scalene)
  end
 
  it 'knows that very small triangles are legal' do
    Triangle.new(0.4, 0.6, 0.3).kind.should eq(:scalene)
  end
 
  # Bonus Tests
  it 'knows that triangles with no size are illegal' do
    expect{Triangle.new(0, 0, 0).kind}.to raise_error(TriangleError)
  end
 
  it 'knows that triangles with negative sides are illegal' do
    expect{Triangle.new(3, 4, -5).kind}.to raise_error(TriangleError)
  end
 
  it 'knows that triangles violating triangle inequality are illegal' do
    expect{Triangle.new(1, 1, 3).kind}.to raise_error(TriangleError)
  end
 
  it 'knows that triangles violating triangle inequality are illegal 2' do
    expect{Triangle.new(2, 4, 2).kind}.to raise_error(TriangleError)
  end
 
  it 'knows that triangles violating triangle inequality are illegal 3' do
    expect{Triangle.new(7, 3, 2).kind}.to raise_error(TriangleError)
  end
 
end