Exercism Ruby Track

Exercism Exercises in Ruby

Setup

You'll need a recent (2.1+) version of Ruby, but that's it. Minitest ships with the language, so you're all set.

Anatomy of an Exercise

The files for an exercise live in exercises/<slug>. The slug for an exercise is a unique nickname composed of a-z (lowercase) and -, e.g. clock or atbash-cipher. Inside its directory, each exercise has:

a test suite, <exercise_name>_test.rb
an example solution, .meta/solutions/<exercise_name>.rb

where <exercise_name> is the underscored version of the exercise's slug, e.g., clock or atbash_cipher.

If the exercise has a test generator, the directory will also contain:

.version
the test generator, .meta/generator/<exercise_name>_case.rb

A few exercises use a custom test template:

.meta/generator/test_template.erb

BookKeeping::VERSION

For some, even perhaps many, of the exercises, you will find a reference to the BookKeeping module, but this is only included when tests have been generated; see Generated Test Suites.

Canonical Data

Most exercises can be generated from shared inputs/outputs, called canonical data (see Generated Test Suites below). To find out whether a test has canonical data, check the problem-specifications repo.

Running the Tests

Run the tests using rake, rather than ruby path/to/the_test.rb. rake knows to look for the example solution and to disable skips. Just tell rake the name of your problem and you are set:

rake test:clock

To pass arguments to the test command, like -p for example, you can run the following:

rake test:clock -- -p

To run a subset of the tests, use a regular expression. For example, if tests exist that are named identical_to_4_places, and identical, then we can run both tests with

rake test:hamming -- -p -n="/identical/"

Note that flags which have an attached value, like above, must take the form -flag=value and if value has spaces -flag="value with spaces".

Generated Test Suites

Generated test suites use the bin/generator cli.

Before using the cli it is recommended you run bundle install from within the ruby directory to install/update any required gems.

While many of the exercises which have canonical data already have generators, some do not. To find out whether an exercise has a generator, run

bin/generate -h

In addition to a usage message, the -h flag lists all exercises with a generator. If a generator is available for your exercise, you can

Regenerate the test suite based on updated canonical data
Make changes to a generated exercise

If not, you will need to implement a new generator

Generated exercises depend on the the shared metadata, which must be cloned to the same directory that contains your clone of the ruby repository:

tree -L 1 ~/code/exercism
├── problem-specifications
└── ruby

Regenerating a Test Suite

From within the ruby directory, run the following command:

bin/generate <slug>

Changing a Generated Exercise

Do not edit <slug>/<exercise_name>_test.rb. Any changes you make will be overwritten when the test suite is regenerated.

There are two reasons why a test suite might change:

the tests need to change (an incorrect expectation, a missing edge case, etc)
there might be issues with the style or boilerplate

In the first case, the changes need to be made to the canonical-data.json file for the exercise, which lives in the problem-specifications repository.

../problem-specifications/exercises/<slug>/
├── canonical-data.json
├── description.md
└── metadata.yml

This change will need to be submitted as a pull request to the problem-specifications repository. This pull request needs to be merged before you can regenerate the exercise.

Changes that don't have to do directly with the test inputs and outputs should be made to the exercise's test case generator, discussed in implementing a new generator, next. Then you can regenerate the exercise with bin/generate <slug>.

Implementing a Generator

An exercise's test case generator class produces the code that goes inside the minitest test_<whatever> methods. An exercise's generator lives in exercises/<slug>/.meta/generator/<exercise_name>_case.rb.

The test case generator is a derived class of ExerciseCase (in lib/generator/exercise_case.rb). ExerciseCase does most of the work of extracting the canonical data. The derived class wraps the JSON for a single test case. The default version looks something like this:

require 'generator/exercise_case'

class <ExerciseName>Case < Generator::ExerciseCase

  def workload
    # Example workload:
    "#{assert} Problem.call(#{input.inspect})"
  end

end

where <ExerciseName> is the CamelCased version of the exercise's slug. This is important, since the generator script will infer the name of the class from <slug>.

This class must provide the methods used by the test template. A default template that most exercises can (and do) use lives in lib/generator/test_template.erb. The base class provides methods for the default template for everything except #workload.

#workload generates the code for the body of a test, including the assertion and any setup required. The base class provides a variety of assertion and helper methods. Beyond that, you can implement any helper methods that you need as private methods in your derived class. See below for more information about the intention of #workload

You don't have to do anything other than implement #workload to use the default template.

If you really must add additional logic to the view template, you can use a custom template. Copy lib/generator/test_template.erb to .meta/generator/test_template.erb under your exercise directory and customize. You may need to create .meta and/or .meta/generator.

Workload philosophy.

Prioritize educational value over expert comprehension and make sure that things are clear to people who may not be familiar with Minitest and even Ruby.

Provide the information the student needs to derive the code to pass the test in a clear and consistent manner. Illustrate the purpose of the individual elements of the assertion by using meaningful variable names.

Example output from the workload method:

detector = Anagram.new('allergy')
anagrams = detector.match(["gallery", "ballerina", "regally", "clergy", "largely", "leading"])
expected = ["gallery", "largely", "regally"]
assert_equal expected, anagrams.sort

Pull Requests

We welcome pull requests that provide fixes to existing test suites (missing tests, interesting edge cases, improved APIs), as well as new problems.

If you're unsure, then go ahead and open a GitHub issue, and we'll discuss the change.

Please submit changes to a single problem per pull request unless you're submitting a general change across many of the problems (e.g. formatting).

You can run (some) of the same checks that we run by running the following tool in your terminal:

bin/local-status-check

If you would like to have these run right before you push your commits, you can activate the hook by running this tool in your terminal:

bin/setup-git-hoooks

Thank you so much for contributing! ✨

Style Guide

We have created a minimal set of guidelines for the testing files, which you can take advantage of by installing the rubocop gem. It will use the configuration file located in the root folder, .rubocop.yml. When you edit your code, you can simply run rubocop -D. It will ignore your example solution, but will gently suggest style for your test code.

The -D option that is suggested is provided to give you the ability to easily ignore the Cops that you think should be ignored. This is easily done by doing # rubocop:disable CopName, where the CopName is replaced appropriately.

For more complete information, see Rubocop.

While lib/generator/exercise_case.rb provides helper functions as discussed above, it remains the responsibility of an exercise's generator to interpret its canonical-data.json data in a stylistically correct manner, e.g. converting string indices to integer indices.

READMEs

Do not add a README or README.md file to the exercise's directory. The READMEs are constructed using shared metadata, which lives in the problem-specifications repo.

Contributing Guide

For an in-depth discussion of how exercism language tracks and exercises work, please see the contributing guide

Ruby icon

The Ruby icon is the Vienna.rb logo, and is used with permission. Thanks Floor Dress :)

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