Test Coverage

In order to focus the testing effort where it is most needed, we have a few ways we track test coverage.


The main one is Codecov. Coverage is visible on this webpage, and displays the total coverage, including unit and integration tests. Codecov is especially interesting for its PR comments. The PR comments, in particular, can easily show which diff lines are being tested and which are not.

However, sometimes Codecov gives too rough estimates, and this is where artifact results come in.

Artifact Results

We also push artifacts, as a result of each CI run. You can access them here:

  1. Click "Details" on one of the CI actions run on your PR (literally any one of the actions is fine, you can also access CI actions runs on any CI)
  2. Click "Summary" on the top left of the opening page
  3. Scroll to the bottom of the page
  4. In the "Artifacts" section, just above the "Summary" section, there is a coverage-html link (there is also coverage-lcov for people who use eg. the coverage gutters vscode integration)
  5. Downloading it will give you a zip file with the interesting files.

In there, you can find:

  • Two -diff files, that contain code coverage for the diff of your PR, to easily see exactly which lines are covered and which are not
  • Two -full folders, that contain code coverage for the whole repository
  • Each of these exists in one unit- variant, that only contains the unit tests, and one integration- variant, that contains all the tests we currently have

To check that your PR is properly tested, if you want better quality coverage than what codecov "requires," you can have a look at unit-diff, because we agreed that we want unit tests to be able to detect most bugs due to the troubles of debugging failing integration tests.

To find a place that would deserve adding more tests, look at one of the -full directories on master, pick one not-well-tested file, and add (ideally unit) tests for the lines that are missing.

The presentation is unfortunately less easy to access than codecov, and less eye-catchy. On the other hand, it should be more precise. In particular, the -full variants show region-based coverage. It can tell you that eg. the ? branch is not covered properly by highlighting it red.

One caveat to be aware of: the -full variants do not highlight covered lines in green, they just highlight non-covered lines in red.