newlines_to_br.rb

#!/usr/bin/env ruby

require 'erb'
require 'active_support'
require 'active_support/core_ext'

def newlines_to_br(s)
  html = "".html_safe
  s.split("\n").each_with_index do |line, idx|
    html << "<br />".html_safe if idx > 0
    html << line
  end

  html
end

TEST_CASES = [
  ["a", "a"],
  ["a\nb", "a<br />b"],
  ["a<div>b", "a&lt;div&gt;b"],
]

TEST_CASES.each do |test_case|
  result = newlines_to_br(test_case[0])
  rendered_string = ERB::Util.html_escape(result)

  expected_result = test_case[1]
  if rendered_string != expected_result
    puts "ERROR: expect #{rendered_string} to equal #{expected_result}"
  else
    puts "PASS"
  end
end