Learn the Reactive Extensions for Ruby (RxRuby) with RxRuby Koans

The Koans walk you along the path to enlightenment in order to learn RxRuby. The goal is to learn the RxRuby library. We also teach you culture. Testing is not just something we pay lip service to, but something we live. It is essential in your quest to learn and do great things in the library.

Structure

The koans are broken out into areas by file, events are covered in about_events.rb, time is introduced in about_time.rb, etc. They are presented in order in the index.rb file.

Each koan builds up your knowledge of RxRuby and builds upon itself.

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.

Installing Ruby

In order to run the koans you need Ruby installed. If you do not already have Ruby set up, please visit the Ruby website to install Ruby.

To verify your installation, in your terminal window simply type:

$ ruby -v

Any response for Ruby with a version number greater than 2.0 should be fine.

Installing the RxRuby Koans

To install the RxRuby Koans, download via Git and add the dependencies via bundle:

$ git clone https://github.com/fteem/RxRubyKoans.git
$ cd RxRubyKoans
[RxRubyKoans ]$ bundle install

The Path to Enlightenment

You can run the tests by calling rake at your terminal window.

[RxRubyKoans] $ rake

Warning

At the moment, all of the test are passing. I am looking for someone with good knowledge of RxRuby to review them. When the review is done, the tests will be fixed to work like a proper Koans test suite.

Red, Green, Refactor

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

With the koans, you will need to run the tests 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 it you will see the following output:

  Observable Streams
    1) simple subscription

  1) Observable Streams simple subscription:
     Error: expected 42 to equal undefined

You have come to the first error. You then open up the about_streams.rb file in your text editor and look at simple subscription:

def test_simple_subscription
  stream = RxRuby::Observable.just(42)
  stream.subscribe {|x| assert_equal(__, x) }
end

You then change __ to 42 and run the tests again. You should now have fixed the error.

Before moving on, think about what you are learning.

In this specific case, ignore everything except the method name and the parts inside the method. The goal is for you to see that if you pass a value to the proper assertion method method, it will either ensure it is true and continue on, or fail if in fact the statement is false.

Note

These koans have been ripped off from RxJSKoans and translated to Ruby. Ping me @fteem for any feedback, questions or complaints.

Also, there are some skipped tests in the code, due to missing methods in RxRuby. If you think this is incorrect (or an error on my side), please open an issue.