"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. It helps to identify areas of the code that are not being tested.
Try running any of the unit tests with test coverage in Test Explorer.
As GovTech uses SHIP-HATS (GitLab) for source code management, it would be handy to know how to create a GitLab CI pipeline.
Here's a handy tutorial for creating your own GitLab CI pipeline.