Trial and Error with Ruby Koans

After reading introductory primers and watching instructional videos for beginners learning Ruby opens a new window , I needed a program that would allow me to test out Ruby concepts for myself. I began practicing Ruby Koans opens a new window , a testing-based program that runs through a variety of Ruby concepts in a trial and error fashion.

Instead of providing problems and requiring that the user figure out the answers, the Koans provide answers to various tests and, using assert_equal, require the user to fill in the blanks and correct the code until the program runs without errors.

The first exercises run through Ruby concepts including strings opens a new window , arrays opens a new window and methods opens a new window .

The exercise About Objects opens a new window was particularly useful for me as a Junior Developer. I had heard time and again that “in Ruby, everything is an object” opens a new window , however I didn’t understand what “being an object” actually entailed. This exercise went through what it means to be an object, specifying that although many items are objects, no two objects are ever exactly the same.

def test_clone_creates_a_different_object
  obj =
  copy = obj.clone

  assert_equal true, obj           != copy
  assert_equal true, obj.object_id != copy.object_id

After the Ruby concept exercises, the Koans culminate in a series of projects that allow the user to apply what they have learned about each concept to complete more complex exercises. One that proved useful to me was the About Triangle Project opens a new window .

This exercise gives the user side lengths of three different triangles, and asks the user to write code to test whether each triangle is equilateral, isosceles or scalene.

  class AboutTriangleProject < Neo::Koan
    def test_equilateral_triangles_have_equal_sides
      assert_equal :equilateral, triangle(2, 2, 2)
      assert_equal :equilateral, triangle(10, 10, 10)

    def test_isosceles_triangles_have_exactly_two_sides_equal
      assert_equal :isosceles, triangle(3, 4, 4)
      assert_equal :isosceles, triangle(4, 3, 4)
      assert_equal :isosceles, triangle(4, 4, 3)
      assert_equal :isosceles, triangle(10, 10, 2)

    def test_scalene_triangles_have_no_equal_sides
      assert_equal :scalene, triangle(3, 4, 5)
      assert_equal :scalene, triangle(10, 11, 12)
      assert_equal :scalene, triangle(5, 4, 2)

The answer combines a number of basic Ruby operators opens a new window , including ==, && and ||, and is a simple exercise to begin thinking about the ways that Ruby can solve more complex problems.

I would highly recommend Ruby Koans to any developer who has some knowledge of Ruby and test-driven development and is looking to learn more.

In our Junior Developer Training Path at OmbuLabs, we typically complete the Ruby Koans after reading a Ruby primer book, such as The Well-Grounded Rubyist opens a new window , to get an understanding of the fundamentals of Ruby. What steps did you take to learn to code? Do you have a great Junior Developer Training Path to recommend? Let us know!