Testing OCaml projects on Travis CI

Update (Oct 2013): Anil  Madhavapeddy has fleshed this out further.

This evening I spent some time getting unit tests for my OCaml projects to run on Travis CI, a free service for continuous integration on public GitHub projects. Although Travis has no built-in OCaml environment, it's straightforward to hijack its C environment to install OCaml and OPAM, then build an OCaml project and run its tests.

1. Perform the initial setup to get Travis CI watching your GitHub repo (up to and including step two of that guide).

2. Add a .travis.yml file to the root of your repo, with these contents:

language: c
script: bash -ex travis-ci.sh

3. Fill in travis-ci.sh, also in the repo root, with something like this:

# OPAM version to install
export OPAM_VERSION=0.9.1
# OPAM packages needed to build tests
export OPAM_PACKAGES='ocamlfind ounit'

# install ocaml from apt
sudo apt-get update -qq
sudo apt-get install -qq ocaml

# install opam
curl -L https://github.com/OCamlPro/opam/archive/${OPAM_VERSION}.tar.gz | tar xz -C /tmp
pushd /tmp/opam-${OPAM_VERSION}
./configure
make
sudo make install
opam init
eval `opam config -env`
popd

# install packages from opam
opam install -q -y ${OPAM_PACKAGES}

# compile & run tests (here assuming OASIS DevFiles)
./configure --enable-tests
make test

4. Add and commit these two new files, and push to GitHub. Travis CI will then execute the tests.

Working examples: ForkWork, yajl-ocaml

Installing OCaml and OPAM add less than two minutes of overhead, leaving plenty of room for your tests within the stated 15-20 minute time limit for open-source builds. I'm sure the above steps could be used as the basis for an eventual OCaml+OPAM environment built-in to Travis CI.