"Test coverage" is used both as a synonym for [code-coverage] and to mean all measures of the extent of testing of a program including both [code-coverage] and [function-coverage].
"Test coverage" is used both as a synonym for code-coverage and to mean all measures of the extent of testing of a program including both code-coverage and function-coverage.
In the latter sense, test coverage measures the amount of testing performed by a set of tests. Wherever we can count things and can tell whether or not each of those things has been tested by some test, then we can measure coverage, known as test coverage.
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Both of the above articles discuss code coverage, not test coverage in the broader sense.