Continuous Integration

You can easily test your website build against one or more versions of Ruby. The following guide will show you how to set up a free build environment on Travis, with GitHub integration for pull requests. Paid alternatives exist for private repositories.

1. Enabling Travis and GitHub

Enabling Travis builds for your GitHub repository is pretty simple:

1. Go to your profile on travis-ci.org: https://travis-ci.org/profile/username
2. Find the repository for which you’re interested in enabling builds.
3. Click the slider on the right so it says “ON” and is a dark grey.
4. Optionally configure the build by clicking on the wrench icon. Further configuration happens in your .travis.yml file. More details on that below.

2. The Test Script

The simplest test script simply runs jekyll build and ensures that Jekyll doesn’t fail to build the site. It doesn’t check the resulting site, but it does ensure things are built properly.

When testing Jekyll output, there is no better tool than html-proofer. This tool checks your resulting site to ensure all links and images exist. Utilize it either with the convenient htmlproof command-line executable, or write a Ruby script which utilizes the gem.

The HTML Proofer Executable

#!/usr/bin/env bash
set -e # halt script on error

bundle exec jekyll build
bundle exec htmlproof ./_site

Some options can be specified via command-line switches. Check out the html-proofer README for more information about these switches, or run htmlproof --help locally.

The HTML Proofer Library

You can also invoke html-proofer in Ruby scripts (e.g. in a Rakefile):

#!/usr/bin/env ruby

require 'html/proofer'
HTML::Proofer.new("./_site").run

Options are given as a second argument to .new, and are encoded in a symbol-keyed Ruby Hash. More information about the configuration options, check out html-proofer’s README file.

3. Configuring Your Travis Builds

This file is used to configure your Travis builds. Because Jekyll is built with Ruby and requires RubyGems to install, we use the Ruby language build environment. Below is a sample .travis.yml file, and what follows that is an explanation of each line.

language: ruby
rvm:
- 2.1
script: ./script/cibuild

# branch whitelist
branches:
  only:
  - gh-pages     # test the gh-pages branch
  - /pages-(.*)/ # test every branch which starts with "pages-"

env:
  global:
  - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer

Ok, now for an explanation of each line:

language: ruby

This line tells Travis to use a Ruby build container. It gives your script access to Bundler, RubyGems, and a Ruby runtime.

rvm:
- 2.1

RVM is a popular Ruby Version Manager (like rbenv, chruby, etc). This directive tells Travis the Ruby version to use when running your test script.

script: ./script/cibuild

Travis allows you to run any arbitrary shell script to test your site. One convention is to put all scripts for your project in the script directory, and to call your test script cibuild. This line is completely customizable. If your script won’t change much, you can write your test incantation here directly:

script: jekyll build && htmlproof ./_site

The script directive can be absolutely any valid shell command.

# branch whitelist
branches:
  only:
  - gh-pages     # test the gh-pages branch
  - /pages-(.*)/ # test every branch which starts with "pages-"

You want to ensure the Travis builds for your site are being run only on the branch or branches which contain your site. One means of ensuring this isolation is including a branch whitelist in your Travis configuration file. By specifying the gh-pages branch, you will ensure the associated test script (discussed above) is only executed on site branches. If you use a pull request flow for proposing changes, you may wish to enforce a convention for your builds such that all branches containing edits are prefixed, exemplified above with the /pages-(.*)/ regular expression.

The branches directive is completely optional.

env:
  global:
  - NOKOGIRI_USE_SYSTEM_LIBRARIES=true # speeds up installation of html-proofer

Using html-proofer? You’ll want this environment variable. Nokogiri, used to parse HTML files in your compiled site, comes bundled with libraries which it must compile each time it is installed. Luckily, you can dramatically decrease the install time of Nokogiri by setting the environment variable NOKOGIRI_USE_SYSTEM_LIBRARIES to true.

4. Gotchas

Exclude vendor

Travis bundles all gems in the vendor directory on its build servers, which Jekyll will mistakenly read and explode on. To avoid this, exclude vendor in your _config.yml:

exclude: [vendor]

Questions?

This entire guide is open-source. Go ahead and edit it if you have a fix or ask for help if you run into trouble and need some help.

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