Published: 30 Apr 2018
Bisect_ppx is a code coverage tool for OCaml. It helps you test thoroughly by showing which parts of your code are not tested. You can also use it for tracing: run one test, and see what is visited.
Most of these commands go in a
Makefile or other script, so that you only have to run that script, then refresh your browser.
opam install bisect_ppx
You can also install without OPAM.
ocamlfind c -package bisect_ppx -c my_code.ml ocamlfind c -c my_tests.ml ocamlfind c -linkpkg -package bisect_ppx my_code.cmo my_tests.cmo
Run your test binary. In addition to testing your code, it will produce one or more files with names like
./a.out # Produces bisect0001.out
Generate the coverage report.
bisect-ppx-report -I _build/ -html coverage/ bisect*.out`
In each file of the report,
Green lines contain expressions, all of which were visited.
Red lines contain expressions, none of which were visited.
Yellow lines contain expressions, some of which were visited, but others not.
White lines are those that don't contain visitable expressions. They may have type declarations, keywords, or something else that Bisect_ppx did not, or cannot instrument.
You can submit a coverage report to Coveralls.io using ocveralls. Note that Bisect_ppx reports are more precise than Coveralls, which only considers whole lines as visited or not.
See also the advanced usage.
Bisect_ppx in practice
A small sample of projects using Bisect_ppx:
Bisect_ppx is available under the Mozilla Public License 2.0 (MPL). To summarize, you can incorporate Bisect_ppx into proprietary projects. If you make modifications to Bisect_ppx, you have to open-source them. The rest of your project remains proprietary.
Essentially, this is like the BSD or MIT licenses, except that if you include a customized Bisect_ppx in a release (as opposed to private use), you have to make the altered source visible. This can be done by contributing the changes back, keeping Bisect_ppx in a visible fork, or if your bigger project itself also happens to be open source.
Besides proprietary licenses, MPL is compatible with BSD/MIT/Apache- and (L)GPL-licensed projects. See the MPL 2.0 FAQ.
The Ocamlbuild plugin is dedicated to the public domain.
Bug reports and pull requests are warmly welcome. Bisect_ppx is developed on GitHub, so please open an issue.
To get the latest development version of Bisect_ppx using OPAM, run
opam source --dev-repo --pin bisect_ppx
You will now have a
bisect_ppx subdirectory to work in.