### Testing packages with R Travis for OS-X

Travis is a continuous integration service which allows for running automated testing code everytime you push to GitHub. Hadley's book about R packages explains how and why R package authors should take advantage of this in their development process.

## The build matrix

Travis is now providing support for multiple operating systems, including Ubuntu 14.04 (Trusty) and various flavors of Mac OS-X. Jim Hester has done a great job of tweaking the travis R-language build script to automate building and checking of R packages on the various platforms.

Cross system testing is mainly useful to check packages with compiled code (i.e. C or C++) against various combinations of compiler versions, external libraries or system services. However any R package can easily be configured to take advantage of these features immediately. It is free and easy to setup!

The R travis options are pretty well documented. The quickest way to get started is by borrowing a .travis.yml configuration from another package. Below a few example packages with a multi-OS build matrix which illustrate various options:

For extra credit also check out the feather package which uses a single platform but has a very cool build matrix targeting multiple compilers with both the python and R interfaces.

## Systems and Libraries

Most configuration options can either be set within or outside the multi-system build matrix (the include field in the yaml). Options which are set outside the matrix apply to each of the systems. If an option is both set within and outside the matrix the former overrides the latter.

The default system on Travis is currently still Ubuntu 12.04 (Precise). To build on Ubuntu 14.04 (Trusty) set the dist and sudo fields:

os: linux
dist: trusty
sudo: required


The sudo field is required to disable the docker environment which currently does not support Trusty yet. This blog post by RStudio has some more information about docker on Travis.

To build on OS-X set the os and osx_image fields:

os: osx
osx_image: xcode8


The osx_image field specifies which version of OS-X and X-code this system has. The Travis OS-X manual lists which combinations are currently available.

## Homebrew

By default all OS-X images include a copy of homebrew. The brew_packages field can be used to install brew packages before building and checking the R package, similar to apt_packages on Linux. See pdftools or sodium for examples.

os: osx
osx_image: xcode8
brew_packages: poppler


Set the disable_homebrew option to specifically test on a system without brew. The following config simulates the CRAN mac-builder machine which runs OS-X Mavericks 10.9:

os: osx
osx_image: beta-xcode6.1
disable_homebrew: true


Besides the version of OS-X and brew packages there are some additional options to customize the config. For example we can customize if Latex should be installed (defaults to true). Latex is huge and annoying so R packages that do not include pdf vignettes can significantly speed up the build process by disabling this.

latex: false


When latex is disabled R CMD check automatically runs with --no-manual to prevent check from failing to build the PDF manual. And while we're add it, to set additional custom R CMD build and R CMD check parameters:

r_build_args: '--no-build-vignettes'
r_check_args: '--ignore-vignettes --no-examples'


The curl config has a real world example. Finally you can put almost anything in the before and after install scripts. Use the TRAVIS_OS_NAME environment variable to run something only on OSX or Linux. An example from jsonlite which installs a custom Latex package:

before_install:
- if [ "\${TRAVIS_OS_NAME}" == "osx" ]; then sudo tlmgr install preprint; fi


Travis R documentation has some more options.

Big thanks to Jim Hester and Craig Citro who have done all this amazing work to get R to work on Travis!