The Free On-line Dictionary of Computing (30 December 2018):
A measure of the proportion of a program exercised
by a test suite, usually expressed as a percentage. This
will typically involve collecting information about which
parts of a program are actually executed when running the test
suite in order to identify which branches of conditional
statements which have been taken.
The most basic level of test coverage is code coverage
testing and the most methodical is path coverage testing.
Some intermediate levels of test coverage exist, but are
The standard Unix tool for measuring test coverage is
tcov, which annotates C or Fortran source with the
results of a test coverage analysis. GCT is a GNU