# 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. Code coverage requires `lcov`; install the tool if necessary by `sudo apt install lcov` or the equivalent for your system. 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. ## Examples `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 `COV=1 make run-unit-tests` runs the unit tests, building them with code coverage if they are out-of-date.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`.