Automating Github Pages and from Travis

With the advent of Travis-ci it has never been easier to setup continuous integration for your Github project. Just sign in to Travis with your...

With the advent of Travis-ci it has never been easier to setup continuous integration for your Github project. Just sign in to Travis with your Github account, enable some repos, profit! It will then build all commits that are pushed to your repo and alert you when you have broken the build. You can even badge your repo with the current build status:


It even tests your pull-requests for you and badges them as passing or failing so you know whether or not to merge:


This is all great, but there’s no reason your Travis job cannot be harnessed to do some other useful stuff! Here we’ll show how use Travis to automatically:

  1. Publish your docs to Github Pages; and
  2. Upload your coverage metrics to

Publishing docs to Github Pages

Building the docs using ocamldoc

The first step is to generate your docs at build time. For OCaml projects using Oasis this is pretty easy and just involves adding a stanza to your _oasis file like this example taken from the ocaml-pci library:

Document pci
  Type:                 ocamlbuild (0.4)
  BuildTools:           ocamldoc
  Title:                API reference for Pci
  XOCamlBuildPath:      .
  XOCamlBuildLibraries: pci

The usual oasis setup dance generates a Makefile with a target to build the docs and so they can be simply generated by:

$ ./configure --enable-docs
$ make doc

Publishing on Github Pages

Github Pages allows for any content pushed to the gh-pages branch of a repository, repo, to be served at https// This is

a very useful feature and can be used to publish documentation for the repository in question. Here’s an example of the documentation page hosted by Github at https// which is just displaying the static HTML that has been push to ocaml-pci#gh-pages.

In order to push from Travis you’ll need to generate an access token which can be done from the Personal access tokens section of your Github settings page:


Once you have this you can encrypt and upload it for use in the Travis build environment:

$ gem install travis
$ travis encrypt -r user/repo GH_TOKEN=<token>
secure: "ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123..."

This then needs adding to your .travis.yml in the env: section:

  - secure: "ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123ABC123..."

This can be made easier if you execute travis from within your repo. This way it can infer the repository and so eliminating the need for the -r option and it can also add it to your .travis.yml for you with the --add flag:

$ travis encrypt GH_TOKEN=<token> --add

Now Travis has a secure token by which it can push to your repository you can now instrument your build job to push for you. Travis sets up some useful environment variables for you in the build VM which can be used to determine whether or not to push the docs. For example, I didn’t want to push the docs if Travis was building a pull-request, only if it was building a commit so I made use of $TRAVIS_PULL_REQUEST. Here’s an example:

set -e
set +x  # Make sure we're not echoing any sensitive data

./configure --enable-docs
make doc

if [ -z "$TRAVIS" -o "$TRAVIS_PULL_REQUEST" != "false" ]; then
  echo "This is not a push Travis-ci build, doing nothing..."
  exit 0
  echo "Updating docs on Github pages..."
if [ -n "$KEEP" ]; then trap "rm -rf $DOCDIR" EXIT; fi
rm -rf $DOCDIR

git clone --quiet --branch=gh-pages https://${GH_TOKEN} $DOCDIR > /dev/null

cp _build/pci.docdir/* $DOCDIR

git -C $DOCDIR config ""
git -C $DOCDIR config "Travis"
git -C $DOCDIR commit --allow-empty -am "Travis build $TRAVIS_BUILD_NUMBER pushed docs to gh-pages"
git -C $DOCDIR push origin gh-pages > /dev/null

That’s it! You just need to get Travis to execute this script for you as part of the job.

Pushing coverage metrics to Coveralls

It’s good to know how much your tests suck! For this it’s handy to know just how much of your program or library your tests actually exercise. Enter



Toys you’ll need in your toybox

Bisect is a code coverage tool for OCaml written by Xavier Clerc. It uses the OCaml preprocessor to add instrumentation points using either camlp4 or the new ppx extension point mechanism. When linked against your project it will spew out files from which it can generate reports in various forms using bisect-report provided in the package.

Ocveralls is a tool that will take Bisect coverage data and produce JSON output suitable for uploading to Coveralls. It also has some smarts to work out what kind of CI it is running on and to send the coverage data directly to Coveralls using the --send flag.

Scripting it for Travis

One of the main things to work around is not wanting to have Bisect linked against your project for normal compilation. If you do then it will run its instrumentation code every time it is executed, even if your project is a library consumed by other projects, linking in Bisect will result in this data being produced *every time your code is executed*.

The workaround for this is not very elegant but it works. During the Travis job you can use sed to add bisect (or bisect_ppx) as a build dependency of your package as a one-off step:

$(which cp) -r ../* .
sed -i '/BuildDepends:/ s/$/, bisect_ppx/' _oasis
oasis setup

./configure --enable-tests

Then you can run your test to generate the coverage data:

find . -name bisect* | xargs rm -f
./test_pci.native -runner sequential

Note the -sequential here. This is because I have used OUnit for my unit tests which spawns off worker threads to execute the test cases. Bisect will generate incomplete results in this case unless the BisectThreads package is linked in.

Once the data has been generated you can use ocveralls --send to push this data to Coveralls:

if [ -n "$TRAVIS" ]; then
  echo "\$TRAVIS set; running ocveralls and sending to"
  ocveralls --prefix _build bisect*.out --send

Done! This script has some extra padding but is used here. Coveralls can then keep track of your coverage over build history:


It can also comment on your pull-request and become part of your gating criteria for merging:


And, of course… where would we be without a gratuitous badge for our repo’s REAMDE?!:


Let the game begin

Now for the quest to keep that coverage creeping up!

Blackpool-born & Cambridge-based. Full-time hacker & Part-time consumer of Dr. Pepper.

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