Programming Ruby 3.3

Testing with Minitest

If all that seems a little abstract, let’s look at an example of how you use the minitest library to write automated testing. We’ll start with a Roman numeral class. Our first pass at the code is pretty simple; it lets us create an object representing a certain number and display that object in Roman numerals:

unittesting/romanbug.rb

# This code has bugs
class Roman
  MAX_ROMAN = 4999

  def initialize(value)
    if value <= 0 || value > MAX_ROMAN
      fail "Roman values must be > 0 and <= #{MAX_ROMAN}"
    end
    @value = value
  end

  FACTORS = [
    ["m", 1000], ["cm", 900], ["d", 500], ["cd", 400],
    ["c", 100], ["xc", 90], ["l", 50], ["xl", 40],
    ["x", 10], ["ix", 9], ["v", 5], ...