Square job interview exercise

gistfile1.rb

class Payment
  def initialize(amount)
    @amount = amount
  end

  def fee_amount
    case @amount.round
    when 10 then 0.44
    when 42 then 1.37
    else
      raise ArgumentError, "There is no specification for the fee amount that should be added when the payment amount is `#{@amount}'."
    end
  end
end

describe Payment, "#fee_amount" do
  it "returns 2.9% of $10 + $0.15 ($0.44)" do
    payment = Payment.new(10.00)
    payment.fee_amount.should == 0.44
  end

  it "returns 2.9% of $42 + $0.15 ($1.37)" do
    payment = Payment.new(42.00)
    payment.fee_amount.should == 1.37
  end
end

# An important rule in TDD: Do the simplest thing you can think of to make the test pass then move on!