Building a Ruby Project

What This Guide Covers

This guide covers build environment and configuration topics specific to Ruby projects. Please make sure to read our Getting Started and general build configuration guides first.

Supported Ruby Versions and RVM

The Ruby VM provides recent versions of:

  • Ruby: 2.2.0, 2.1.x, 2.0.0, 1.9.3, 1.9.2 and 1.8.7
  • JRuby: 1.7.x (1.8 and 1.9 mode)
  • Ruby Enterprise Edition: 1.8.7 2012.02

Pre-compiled versions are downloaded on demand from our Ruby version cache.

Pre-compiled Rubinius versions are downloaded on demand from Older versions of Ruby and JRuby are made available by RVM and the JRuby team.

For exact version information, consult the “Build system information” section of the build log.

Choosing Ruby versions and implementations to test against

The Ruby environment on Travis CI uses RVM to provide many Ruby implementations and versions your projects can be tested against.

To specify them, use rvm: key in your .travis.yml file, for example:

language: ruby
  - 2.2
  - jruby
  - rbx-2

Note that the rvm: key is only available in Ruby Build Environments, not in other images containing a ruby implementation.

As we upgrade both RVM and Rubies, aliases like 2.2 or jruby point to different exact versions, patch levels and so on.

For a full up-to-date list of provided Rubies, see our CI environment guide.

If you don’t specify a version, Travis CI will use MRI 1.9.3 as the default.

When using Rubinius, there’s currently an issue with selecting the correct version in RVM in our build environment, but only when specifying rbx as your version. As a workaround, specify rbx-2 instead.

Using .ruby-version

If the ruby version is not specified by the rvm key as described above, Travis CI will consult .ruby-version in the root of the repository and use the indicated Ruby runtime.

Choosing Rubies that aren’t installed

While we pre-install some Rubies, you can install other versions by way of RVM’s binary installation feature.

As long as they’re available as a binary for Ubuntu 12.04, you can specify custom patchlevels.

language: ruby
  - 2.0.0-p247

Note that this binds you to potentially unsupported releases of Rubies. It also extends your build time as downloading and installing a custom Ruby can add an extra 60 seconds or more to your build.


Rubinius releases frequent updates. Binaries for Travis CI should be available for every release from 2.1.1 onwards. To test against a release of Rubinius, add rbx-X.Y.Z to your .travis.yml, where X.Y.Z specifies a Rubinius release.

Note that the syntax of rbx-19mode isn’t supported anymore.

Rubinius will be installed via a download currently.

JRuby: C extensions support is disabled

Please note that C extensions are disabled for JRuby on Travis CI. The reason for doing so is to bring it to developers attention that their project may have dependencies that should not be used on JRuby in production. Using C extensions on JRuby is technically possible but is not a good idea performance and stability-wise and we believe continuous integration services like Travis CI should highlight it.

So if you want to run CI against JRuby, please check that your Gemfile takes JRuby into account. Most of popular C extensions these days also have Java implementations (json gem, nokogiri, eventmachine, bson gem) or Java alternatives (like JDBC-based drivers for MySQL, PostgreSQL and so on).

Default Test Script

Travis CI runs rake by default to execute your tests. Please note that you need to add rake to your Gemfile (adding it to the :test group should be sufficient).

Dependency Management

Travis CI uses Bundler

Travis CI uses Bundler to install your project’s dependencies.

The default command run by Travis CI is:

bundle install --jobs=3 --retry=3

Note that this is only run when we detect a Gemfile in the project’s root directory, or if the Gemfile specified via the build matrix exists.

If a Gemfile.lock exists in your project’s root directory, we add the --deployment flag.

If you want to use a different means of handling your Ruby project’s dependencies, you can override the install command.

install: gem install rails

By default, gems are installed into vendor/bundle in your project’s root directory.

Caching Bundler

Bundler installation can take a while, slowing down your build. You can tell Travis CI to cache the installed bundle.

On your first build, we warm the cache. On the second one, we’ll pull in the cache, making bundle install only take seconds to run.

Note that this feature is currently only available for private projects.

Speeding up your build by excluding non-essential dependencies

Lots of project include libraries like ruby-debug, unicorn or newrelic_rpm in their default set of gems.

This slows down the installation process quite a lot, and commonly, those libraries aren’t needed when running your tests. This also includes libraries that compile native code, slowing down the installation and overall test times even more.

On top of that, libraries that implicitly pull in ruby_core_source or linecache19, are bound to fail when Travis CI upgrades Ruby versions and patchlevels.

The same is true for gems that you only need in production, like Unicorn, the New Relic library, and the like.

You can speed up your installation process by moving these libraries to a separate section in your Gemfile, e.g. production:

group :production do
  gem 'unicorn'
  gem 'newrelic_rpm'

Adjust your Bundler arguments to explicitly exclude this group:

bundler_args: --without production

Enjoy a faster build, which is also less prone to compilation problems.

Custom Bundler arguments and Gemfile locations

You can specify a custom Gemfile name:

gemfile: gemfiles/

Unless specified, the worker will look for a file named “Gemfile” in the root of your project.

You can also set extra arguments to be passed to bundle install:

bundler_args: --binstubs

You can also define a script to be run before ‘bundle install’:

before_install: some_command

For example, to install and use the pre-release version of bundler:

before_install: gem install bundler --pre

Testing against multiple versions of dependencies

Many projects need to be tested against multiple versions of Rack, EventMachine, HAML, Sinatra, Ruby on Rails,etc.

To test against multiple versions of dependencies:

  1. Create a directory in your project’s repository root where you will keep gemfiles (./gemfiles is a commonly used name)
  2. Add one or more gemfiles to it
  3. Instruct Travis CI to use those gemfiles using the gemfile option in your .travis.yml

For example, amqp gem is tested against EventMachine 0.12.x and 1.0 pre-releases:

  - Gemfile
  - gemfiles/eventmachine-pre

Thoughtbot’s Paperclip is tested against multiple ActiveRecord versions:

  - gemfiles/rails2.gemfile
  - gemfiles/rails3.gemfile
  - gemfiles/rails3_1.gemfile

An alternative to this is to use environment variables and make your test runner use them. For example, Sinatra is tested against multiple Tilt and Rack versions:

  - "rack=1.3.4"
  - "rack=master"
  - "tilt=1.3.3"
  - "tilt=master"

ChefSpec is tested against multiple Opscode Chef versions:

  - CHEF_VERSION=0.9.18
  - CHEF_VERSION=0.10.2
  - CHEF_VERSION=0.10.4

The same technique is often applied to test against multiple databases, templating engines, hosted service providers and so on.

$BUNDLE_GEMFILE environment variable

When gemfile is thus defined and the file exists in the repository, we define the environment variable $BUNDLE_GEMFILE, which bundle install uses to resolve dependencies.

If you need to work with multiple Gemfiles within a single job, you would need to override $BUNDLE_GEMFILE by passing --gemfile= flag:

bundle install --gemfile=my_gemfile

Testing against multiple JDKs (JRuby)

It is possible to test projects against multiple JDKs, namely

  • OpenJDK 7
  • Oracle JDK 7
  • Oracle JDK 8
  • OpenJDK 6

To do so, use the jdk key in your .travis.yml, for example:

  - oraclejdk7
  - openjdk7

or all 4:

  - openjdk7
  - oraclejdk7
  - oraclejdk8
  - openjdk6

Each JDK you test against will create permutations with all other configurations, so to avoid running tests for, say, CRuby 1.9.3 multiple times you need to add some matrix excludes (described in our general Build Configuration guide):

language: ruby
  - 1.9.2
  - jruby-18mode
  - jruby-19mode
  - jruby-head
  - openjdk6
  - openjdk7
  - oraclejdk7
    - rvm: 1.9.2
      jdk: openjdk6
    - rvm: 1.9.2
      jdk: openjdk7
    - rvm: 1.9.2
      jdk: oraclejdk7

For example, see travis-support.

Upgrading RubyGems

The RubyGems version installed on Travis CI’s Ruby environment depends on what’s installed by the newest Bundler/RubyGems combination.

We try to keep it as up-to-date as possible.

Should you require the latest version of RubyGems, you can add the following to your .travis.yml:

  - gem update --system
  - gem --version

If you need to downgrade to a specific version, you can use the following steps:

  - gem update --system 2.1.11
  - gem --version

Note that this will impact your overall test time, as additional network downloads and installations are required.

Build Matrix

For Ruby projects, env, rvm, gemfile, and jdk can be given as arrays to construct a build matrix.