3 Variations of Spec Files

custom_assertion_spec.rb

require './numeral_converter'
require 'minitest/autorun'

describe NumeralConverter do
  describe "#to_roman" do
    it "converts 1 to I" do
      1.must_equal_roman "I"
    end
    it "converts 2 to II" do
      2.must_equal_roman "II"
    end
    it "converts 5 to V" do
      5.must_equal_roman "V"
    end
  end
end

module Minitest::Assertions
  def assert_equals_roman(roman, integer)
    assert NumeralConverter.to_roman(integer) == roman, "Expected #{integer} to convert to #{roman}"
  end
end

Numeric.infect_an_assertion :assert_equals_roman, :must_equal_roman

let_spec.rb

require './numeral_converter'
require 'minitest/autorun'

describe NumeralConverter do
  describe "#to_roman" do
    let(:roman) { NumeralConverter.to_roman(arabic) }
    describe "with 1" do
      let(:arabic) { 1 }
      it { roman.must_equal "I" }
    end
    describe "with 2" do
      let(:arabic) { 2 }
      it { roman.must_equal "II" }
    end
    describe "with 5" do
      let(:arabic) { 5 }
      it { roman.must_equal "V" }
    end
  end
end

normal_spec.rb

require './numeral_converter'
require 'minitest/autorun'

describe NumeralConverter do
  describe "#to_roman" do
    it "converts 1 to I" do
      NumeralConverter.to_roman(1).must_equal "I"
    end
    it "converts 2 to II" do
      NumeralConverter.to_roman(2).must_equal "II"
    end
    it "converts 5 to V" do
      NumeralConverter.to_roman(2).must_equal "II"
    end
  end
end

numeral_converter.rb

module NumeralConverter
  def self.to_roman(numeral)
    "I" * numeral
  end
end