Unit Test Code Coverage

Code coverage for the coreboot unit tests allows us to see what lines of code in the coreboot library are covered by unit tests, and allows a test author to see where they need to add test cases for additional coverage.

Enable code coverage in your unit test build by setting the environment variable COV to 1; either export COV=1 in your shell, or add it to your make command, e.g. COV=1 make unit-tests.

The build output directory is either build/tests or build/coverage, depending on whether COV=1 is set in the environment.

All of the unit test targets are available with and without COV=1

  • clean-unit-tests
  • build-unit-tests
  • run-unit-tests
  • unit-tests (which is just build-unit-tests followed by run-unit-tests)

There are two new make targets:

  • coverage-report generates a code coverage report from all of the GCOV data (*.gcda and *.gcno files) in the build directory. To view the coverage report, open build/coverage/coverage_reports/index.html in your web browser.
  • clean-coverage-report deletes just the coverage report.

The coverage-report and clean-coverage-report targets automatically set COV=1 if it is not already set in the environment.


COV=1 make unit-tests coverage-report builds all of the unit tests with code coverage, runs the unit tests, and generates the code coverage report.

COV=1 make build-unit-tests builds all of the unit tests with code coverage.

COV=1 make run-unit-tests runs the unit tests, building them with code coverage if they are out-of-date.

COV=1 make coverage-report creates the code coverage report. This target does not explicitly depend on the tests being built and run; it gathers the code coverage data from the output directory, which it assumes already exists.

COV=1 make tests/lib/uuid-test coverage-report builds the uuid test with code coverage, runs it, and generates a code coverage report just for that test.

As a demonstration that building with and without coverage uses different output directories:

  1. make build-unit-tests builds unit tests without code coverage into build/tests.
  2. COV=1 make clean-unit-tests cleans build/coverage
  3. make build-unit-tests doesn’t need to build anything in build/tests, because those files weren’t affected by the previous clean-unit-tests.