Fibonaci Sequence Generator 1

fibonaci_sequence_generator.rb

class FibonaciSequenceGenerator
  class SequenceToLongError < StandardError; end

  def generate(length)
    raise SequenceToLongError if length > 50

    @sequence = []
    1.upto(length) {|number| @sequence << fibonaci_number(number)}
    @sequence
  end

  def fibonaci_number(number)
    case number
    when 1 then 0
    when 2 then 1
    else @sequence[number - 2] + @sequence[number - 3]
    end
  end
end

fibonaci_sequence_generator_spec.rb

describe FibonaciSequenceGenerator do
  let(:generator){ FibonaciSequenceGenerator.new }

  it "contains 0 as the first number in a sequence" do
    generator.generate(8).first.should be == 0
  end

  it "contains 1 as the second number in a sequence" do
    generator.generate(8)[1].should be == 1
  end

  it "contains 1 as the third number in a sequence" do
    generator.generate(8)[2].should be == 1
  end

  it "contains 2 as the fourth number in a sequence" do
    generator.generate(8)[3].should be == 2
  end

  it "limits the length to 50" do
    lambda{ generator.generate(51) }.should raise_error FibonaciSequenceGenerator::SequenceToLongError
  end
end

Feel like I should have refactored my tests :/ Well next time..