Some time ago Ben Smith added test coverage reports using GCC -fprofile-arcs -
ftest-coverage and lcov.

It reports code coverage after running "make test". Reported code coverage is 
surprisingly high for the very little code executed by "make test" - create ODB, 
start a frontend,  start run, stop run, check that mlogger created data files 
and history files.

(Of course coverage can never reach 100%, some obscure branches are unreachable 
without using an automated fuzzer, and some error paths are unreachable without 
also using a system call fault injector).

Simplest way to generate a coverage report:

make clean
make cmake YES_COVERAGE=1
make coverage
open cov_html/index.html

K.O.