When we want to do stuff repeatedly, we use loops. There are many ways to create loops in Ruby, and here we're going to see the simplest method.

In this chapter we're going to write a method that adds some sort of an underline in a string with the = character, like this:

this is a string
================

As usual, let's start with the test.

Write the test first

Falar sobre o heredoc (mostrar link pra documentação).

require 'minitest/autorun'
require_relative 'underline'

class TestUnderline < Minitest::Test
  def test_underline
    expected = <<~TEXT
      this is a string
      ================
    TEXT
    actual = underline('this is a string')

    assert_equal expected, actual
  end
end

Write the minimal amount of code for the test to run

Keep the discipline! You don't need to know anything new right now to make the test fail properly.

All you need to do right now is enough to make the test fail with no errors.

So, create a file named underline.rb with this code:

def underline(text)
  ""
end

Run the test and it should fail with no errors.

Write enough code to make the test pass

In order to solve this we need:

• a way to check how many characters there are in a string,
• a way to print the = character the same amount of times.

Refactor

def underline(text)
  "#{text}\n#{'=' * text.length}\n"
end

Repeat for new requirements

Key Concepts