DMS Ruby Koans

The Ruby Koans walk you along the path to enlightenment in order to learn Ruby. The goal is to learn the Ruby language, syntax, structure, and some common functions and libraries. We also teach you culture by basing the koans on tests. Testing is not just something we pay lip service to, but something we live. Testing is essential in your quest to learn and do great things in Ruby.

Installing Ruby

If you do not have Ruby setup, please visit http://ruby-lang.org/en/downloads/ for operating specific instructions. In order to run the koans you need ruby and rake installed. To check your installations simply type:

*nix platforms from any terminal window:

[~] $ ruby --version
[~] $ rake --version

Windows from the command prompt (cmd.exe)

c:\ruby --version
c:\rake --version

If you don't have rake installed, run the command gem install rake

Any response for Ruby with a version number greater than 1.8 is fine. Any version of rake will do.

Clone the Koans Repository

Cloning the repository will put the necessary files on your computer:

$ git clone https://github.com/<organization>/ruby-koans-<username>.git ruby_koans

and create a dedicated branch:

$ cd ruby_koans
$ git checkout -b my_branch

It doesn't matter much what name you use, because this branch will only exist on your local computer and your personal repository on GitHub. It won't be part of the Koans Git repository.

The Structure

The koans are broken out into areas by file, hashes are covered in about_hashes.rb, modules are introduced in about_modules.rb, etc. They are presented in order in the path_to_enlightenment.rb file.

Each koan builds up your knowledge of Ruby and builds upon itself. It will stop at the first place you need to correct.

Some koans simply need to have the correct answer substituted for an incorrect one. Some, however, require you to supply your own answer. If you see the method __ (a double underscore) listed, it is a hint to you to supply your own code in order to make it work correctly.

The Path To Enlightenment

You can run the tests through rake or by calling the file itself (rake is the recommended way to run them as we might build more functionality into this task).

*nix platforms, from the ruby_koans directory

[ruby_koans] $ rake                           # runs the default target :walk_the_path
[ruby_koans] $ ruby path_to_enlightenment.rb  # simply call the file directly

Windows is the same thing

c:\ruby_koans\rake                             # runs the default target :walk_the_path
c:\ruby_koans\ruby path_to_enlightenment.rb    # simply call the file directly

Red, Green, Refactor

In test-driven development the mantra has always been red, green, refactor. Write a failing test and run it (red), make the test pass (green), then look at the code and consider if you can make it any better (refactor).

While walking the path to Ruby enlightenment you will need to run the koan and see it fail (red), make the test pass (green), then take a moment and reflect upon the test to see what it is teaching you and improve the code to better communicate its intent (refactor).

The very first time you run the koans you will see the following output:

[ruby_koans] $ rake
(in /Users/person/dev/ruby_koans)
/usr/bin/ruby1.8 path_to_enlightenment.rb

AboutAsserts#test_assert_truth has damaged your karma.

The Master says:
You have not yet reached enlightenment.

The answers you seek...
<false> is not true.

Please meditate on the following code:
./about_asserts.rb:10:in `test_assert_truth'
path_to_enlightenment.rb:38:in `each_with_index'
path_to_enlightenment.rb:38

mountains are merely mountains
your path thus far [X_________________________________________________] 0/282

You have come to your first stage. Notice it is telling you where to look for the first solution:

Please meditate on the following code:
./about_asserts.rb:10:in `test_assert_truth'
path_to_enlightenment.rb:38:in `each_with_index'
path_to_enlightenment.rb:38

Open the about_asserts.rb file and look at the first test:

# We shall contemplate truth by testing reality, via asserts.
def test_assert_truth
  assert false                # This should be true
end

Change the false to true and re-run the test. After you are done, think about what you are learning. In this case, ignore everything except the method name (test_assert_truth) and the parts inside the method (everything before the end).

In this case the goal is for you to see that if you pass a value to the assert method, it will either ensure it is true and continue on, or fail if the statement is false.

Atomic Commits

After each koan is solved, you should commit and push your solution to the remote repository. A typical workflow is as follows:

git status
git add about_asserts.rb
git commit -m "solves assert truth"
git push origin my_branch:my_branch

Alternatively, you can atomic commit in one succint step:

git commit -am "solves assert truth" && git push

If you'd rather group a unit of work on a "per file" basis, you can add each koan solution to the staging index, and then commit and push:

git add about_asserts.rb
...
git add about_asserts.rb
git commit -m "completes the about_asserts koans"
git push origin my_branch:my_branch

After you have solved all the koans, merge your branch into master and push it to the remote repository:

git checkout master
git merge my_branch
git push origin master:master

Bypassing the Projects

This section is optional.

If you're pressed for time, consider bypassing the three projects using these quick solutions:

about_triangle_project.rb
about_scoring_project.rb
about_dice_project.rb

Running the Koans automatically

This section is optional.

Normally the path to enlightenment looks like this:

cd ruby_koans
rake
# edit
rake
# edit
rake
# etc

If you prefer, you can keep the koans running in the background so that after you make a change in your editor, the koans will immediately run again. This will hopefully keep your focus on learning Ruby instead of on the command line.

Install the Ruby gem (library) called watchr and then ask it to "watch" the koans for changes:

cd ruby_koans
rake
# decide to run rake automatically from now on as you edit
gem install watchr
watchr ./koans/koans.watchr

Inspiration

A special thanks to Mike Clark and Ara Howard for inspiring this project. Mike Clark wrote an excellent blog post about learning Ruby through unit testing. This sparked an idea that has taken a bit to solidify, that of bringing new rubyists into the community through testing. Ara Howard then gave us the idea for the Koans in his ruby quiz entry on Meta Koans (a must for any rubyist wanting to improve their skills). Also, "The Little Lisper" taught us all the value of the short questions/simple answers style of learning.

Mike Clark's post
Meta Koans
The Little Lisper