Solution to Triangle Classification Challenge from http://onestepback.org/vital_testing/

TriangleClassification.rb

require 'rspec'

class TriangleClassifier
  def classify(len1, len2, len3)
    lengths = [len1, len2, len3].sort
    raise ArgumentError unless lengths.select {|length| length <= 0}.empty?
    raise ArgumentError unless lengths[0] + lengths[1] > lengths[2]
    case lengths.uniq.count
      when 3 then :scalene
      when 2 then :isoceles
      when 1 then :equilateral
    end
  end
end
  
describe TriangleClassifier do
  before(:each) do
    @classifier = TriangleClassifier.new
  end
  
  it "returns scalene if all three sides are different lengths" do
    @classifier.classify(3, 4, 5).should == :scalene
    @classifier.classify(50, 87, 94).should == :scalene
    @classifier.classify(307, 9, 308).should == :scalene
  end
  
  it "returns isoceles if two sides are equal lengths" do
    @classifier.classify(3, 3, 5).should == :isoceles
    @classifier.classify(4, 6, 4).should == :isoceles
    @classifier.classify(2, 200, 200).should == :isoceles
  end
  
  it "returns equilateral if all three sides are equal lengths" do
    @classifier.classify(3, 3, 3).should == :equilateral
    @classifier.classify(1, 1, 1).should == :equilateral
    @classifier.classify(170, 170, 170).should == :equilateral
  end
  
  it "raises ArgumentError if any given length is less than or equal to 0" do
    lambda {@classifier.classify(3, 2, 0)}.should raise_error ArgumentError
    lambda {@classifier.classify(4, 4, -4)}.should raise_error ArgumentError
    lambda {@classifier.classify(0, 0, 0)}.should raise_error ArgumentError
  end
  
  it "raises ArgumentError if the sum of two lengths are not greater than the third" do
    lambda {@classifier.classify(1, 2, 3)}.should raise_error ArgumentError
    lambda {@classifier.classify(50, 87, 402)}.should raise_error ArgumentError
    lambda {@classifier.classify(307, 9, 117)}.should raise_error ArgumentError
  end
end