Code Coverage

In computer science, test coverage is a measure used to describe the degree to which the source code of a program is executed when a particular test suite runs. A program with high test coverage, measured as a percentage, has had more of its source code executed during testing, which suggests it has a lower chance of containing undetected software bugs compared to a program with low test coverage. (Wikipedia)

This chapter describes how to generate a traditional code coverage report over the Kotlin, Swift and Python code in the Glean SDK repository. To learn how to generate a coverage report about what metrics your project is testing, see the user documentation on generating testing coverage reports.

Generating Kotlin reports locally

Locally you can generate a coverage report with the following command:

./gradlew -Pcoverage :glean:build

After that you'll find an HTML report at the following location:


Generating Swift reports locally

Xcode automatically generates code coverage when running tests. You can find the report in the Report Navigator (View -> Navigators -> Show Report Navigator -> Coverage).

Generating Python reports locally

Python code coverage is determined using the library.


make coverage-python

to generate code coverage reports in the Glean virtual environment.

After running, the report will be in htmlcov.