Bisect_ppx is a code coverage tool for OCaml. It helps you test
thoroughly by showing which parts of your code are *not* tested. It is
a small preprocessor that inserts instrumentation at places in your
code, such as if-then-else and match expressions. After you run tests,
Bisect_ppx gives a nice HTML report showing which places were visited
and which were missed.

Usage is simple - add package bisect_ppx when building tests, run your
tests, then run the Bisect_ppx report tool on the generated visitation
files.