Append the following install stanza of your .travis.yml:

install:
  ...
  - wget https://raw.githubusercontent.com/simonjbeaumont/ocaml-travis-coveralls/master/travis-coveralls.sh

and add the following to your the script stanza:

script: ... && bash travis-coveralls.sh

0. Your project builds with OCaml >= 4.02;
1. Your project is enabled on Coveralls.io; and
2. Your project is configured using Oasis.

The dependency on Oasis allows this tool to link in Bisect_ppx (the OCaml tool for collecting coverage metrics) in a predictable way.

You can configure the commands used to build and what commands are measured by setting the following environment variables in your .tavis.yml:

• $COV_CONF: The command used to configure your project, maybe to enable any tests that are not built by default. This defaults to a no-op;
• $COV_BUILD: The command used to build your project. This defaults to make;
• $COV_TEST: The command under inspection of the coverage tools. Defaults to make test.

For example, if you need to enable tests with a configure script option you can set the following:

env:
  global:
    ...
    - COV_CONF="./configure --enable-tests"

You can also exclude portions of code from coverage metric collection by adding a .coverage.excludes file to your repo. For example if you wanted to exclude the entire contents of some autogenerated files you could add the following to a .coverage.excludes:

file "lib/ffi_generated.ml" [ regexp ".*" ];
file "lib/ffi_generated_types.ml" [ regexp ".*" ];

You can also use this script to see your coverage metrics locally. The script detects that it is not running on Travis and instead outputs the information to stdout and also generates a HTML report.

$ wget https://raw.githubusercontent.com/simonjbeaumont/ocaml-travis-coveralls/master/travis-coveralls.sh
$ bash travis-coveralls.sh
...
Ran: 27 tests in: 0.01 seconds.
OK
$TRAVIS not set; displaying results of bisect-report...
...[ snip ]...
File 'lib/request.ml':
 - 'binding' points: 77/124 (62.10%)
 - 'sequence' points: 2/2 (100.00%)
 - 'for' points: none
 - 'if/then' points: 3/6 (50.00%)
...[ snip ]...
Summary:
 - 'binding' points: 328/637 (51.49%)
 - 'sequence' points: 34/94 (36.17%)
 - 'for' points: 1/1 (100.00%)
 - 'if/then' points: 29/85 (34.12%)
 - 'try' points: 1/1 (100.00%)
 - 'while' points: none
 - 'match/function' points: 124/180 (68.89%)
 - 'class expression' points: none
 - 'class initializer' points: none
 - 'class method' points: none
 - 'class value' points: none
 - 'toplevel expression' points: 1/1 (100.00%)
 - 'lazy operator' points: 4/4 (100.00%)
 - total: 522/1003 (52.04%)

The following Makefile snippet may come in useful to provide a make coverage target that can be run locally:

travis-coveralls.sh:
	wget https://raw.githubusercontent.com/simonjbeaumont/ocaml-travis-coveralls/master/$@

coverage: travis-coveralls.sh
	bash $<

For an example of using this tool and its features, check out the following Github users' projects:

• xapi-project: message-switch, ocaml-crc, xenvm;
• mirage: mirage-block-volume;
• djs55: ocaml-9p;
• johnelse: ocaml-irc-client;
• simonjbeaumont: ocaml-pci.