- Reviewing tests coverage reports
- Reviewing the merge request title
- Reviewing the merge request labels
This document contains rules and suggestions for GitLab Runner project reviewers.
In the GitLab Runner project, we have a lot of code. Unfortunately, the code coverage is not comprehensive. Currently, (early 2019), the coverage is on the level of ~55%.
While adding tests to a legacy code is a hard task, we should ensure that new code that is being added to the project has good tests coverage. Code reviewers are encouraged to look on the coverage reports and ensure new code is covered.
We should aim for as much test coverage for new code as possible. Defining the level of required coverage for a specific change is left for the reviewer judgment. Sometimes 100% coverage will be something simple to achieve. Sometimes adding code with only 20% of the coverage will be realistic and will ensure that the most important things are being tested. Dear reviewer - chose wisely :)
Getting back to the technical details…
The GitLab Runner CI/CD pipeline helps us here and provides the coverage reports in HTML format, for tests
executed in regular (
count) and race (
We have two types of the reports: containing
.regular as part of the file name.
The files are tracking output of
go test command executed with coverage options. The
contain sources and reports for tests started with
-race flag, while the
.regular. files are sources
and reports for tests started without this option.
For those who are interested in details, the
-race tests are using
atomic coverage mode, while the standard
tests are using
count coverage mode.
For our case, the
coverage/coverprofile.regular.html file is what we should look at.
.race. tests can fail
in race condition situations (this is why we’re executing them) and currently we have several of them that
are constantly failing. This means that the coverage profile may not be full.
.regular. tests, instead, should give us the full overview of what’s tested inside our code.
To view a code coverage report for a merge request:
In the merge request’s Overview tab, under the pipeline result, click on View exposed artifact to expand the section.
Click on Code Coverage.
Use the artifact browser to navigate to the
out/coverage/directory. For example, https://gitlab.com/gitlab-org/gitlab-runner/-/jobs/172824578/artifacts/browse/out/coverage/. This directory will always contain six files - three
.race.files and three
For reviewing changes, we’re mostly interested in looking at the
.regular.HTML report (the
coverprofile.regular.htmlfile). As you can see, all files are visible as external links, so for our example we will open https://gitlab.com/gitlab-org/gitlab-runner/-/jobs/172824578/artifacts/file/out/coverage/coverprofile.regular.html which will redirect us to https://gitlab-org.gitlab.io/-/gitlab-runner/-/jobs/172824578/artifacts/out/coverage/coverprofile.regular.html where the report is stored.
The coverage data should be also visible in the merge request UI.
Because we generate
from the merge request titles, making sure that the title is valid and informative is a part
of the reviewer and maintainer’s responsibilities.
Before merging a merge request, check the title and update it if you think it will not be clear in the
CHANGELOG.md file. Keep in mind that the changelog will have only this one line, without the merge
request description, discussion or diff that provide more context.
As an example, look at https://gitlab.com/gitlab-org/gitlab-runner/-/merge_requests/1812 and compare:
yml to yaml- which is the original title and was added to changelog with our script,
Fix values.yaml file name in documentation- which is what I’ve updated it to in the changelog.
yml to yaml tell a GitLab Runner administrator if they review the changelog before updating
to a newer version? Does it show the risks behind the update, the implemented behavior changes, a new
behavior/features that were added? Keep these questions in mind when reviewing the merge request and its title.
Contributors may not be aware of the above information, and that their titles may not match our requirements. Try to educate the contributor about this.
In the end, it’s your responsibility to verify and update the title before the merge request is merged.
We use labels assigned to merge requests to group changelog entries in different groups and define some special features of individual entries.
There are few important things that the reviewer should know about Changelog generator:
GitLab Changelog analyzes merge request labels in the order in which
label_matchersare defined. First matched scope is used for the analyzed merge request.
For example, if there would be two merge request - first one containing labels
bug, second one containing only the
buglabel - and there would be three matchers defined in this order:
[security, bug] -> [security] -> [bug], then the first merge request would be added to the scope matched by
[security, bug](so the first defined on the list) and the second merge request would be added to the scope matched by
[bug](so the last defined scope on the list).
Merge requests labeled with labels defined at
authorship_labelswill be added to the changelog with the author’s username added at the end. All
authorship_labelslabels need to be added to the merge request for it to be marked in this way.
Merge requests labeled with labels defined at
skip_changelog_labelswill be skipped in the changelog. All
skip_changelog_labelslabels need to be added to the merge request for it to be skipped.
Merge request not matching any of the defined
label_matchersare added to the
Other changesscope bucket.
Having all of that in mind, please follow these few rules when merging the merge request:
Any merge request related to how GitLab Runner or its parts are distributed should be labeled with the
Any merge request that touches security - no matter if it’s a new feature or a bug fix - should have the
securitylabel. All merge requests that are not
feature::additionwill be then added to the security scope.
Any bug fix merge request should have the
In most merge requests that are not documentation update only or explicitly a bug fix, make sure that one of the
tooling::labels is added. This will help us sort the changelog entries properly.
documentationlabel is added automatically when the Technical Writing review is done. Even when the merge request updates more than only documentation. If the merge request has only the
documentationlabel and doesn’t have any other label matching any of the defined
label_matchers- double check that the merge request updates the documentation only. Otherwise use one of the specific labels matching the type of the change that is being added!
When you revert a change that was merged during the same release cycle, label the original merge request and the revert one with labels defined in
skip_changelog_labels. This will reduce the manual work that release manager needs to do when preparing the release. We should not add entries about adding a change and reverting the change if both events happened in the same version.
If the revert merge request reverts something, that was merged to an already release version of GitLab Runner, just make sure to label it with the right scope labels. In that case we want to mark the revert in the changelog.
Please also take a moment to read through Engineering metrics data classification page, which gives some guidance about when certain labels should be used.
Dear reviewer, you’ve got your sword. Now go fight with the dragons!