Documentation testing

GitLab documentation is stored in projects with code and treated like code. Therefore, we use processes similar to those used for code to maintain standards and quality of documentation.

We have tests:

  • To lint the words and structure of the documentation.
  • To check the validity of internal links within the documentation suite.
  • To check the validity of links from UI elements, such as files in app/views files.

For the specifics of each test run in our CI/CD pipelines, see the configuration for those tests in the relevant projects:

Run tests locally

Similar to previewing your changes locally, you can also run these tests on your local computer. This has the advantage of:

  • Speeding up the feedback loop. You can know of any problems with the changes in your branch without waiting for a CI/CD pipeline to run.
  • Lowering costs. Running tests locally is cheaper than running tests on the cloud infrastructure GitLab uses.

To run tests locally, it’s important to:

Lint checks

Lint checks are performed by the script and can be executed as follows:

  1. Navigate to the gitlab directory.
  2. Run:

    MD_DOC_PATH=path/to/ scripts/

Where MD_DOC_PATH points to the file or directory you would like to run lint checks for. If you omit it completely, it defaults to the doc/ directory. The output should be similar to:

=> Linting documents at path /path/to/gitlab as <user>...
=> Checking for cURL short options...
=> Checking for duplicate entries...
=> Checking /path/to/gitlab/doc for executable permissions...
=> Checking for new files...
=> Linting markdown style...
=> Linting prose...
✔ 0 errors, 0 warnings and 0 suggestions in 1 file.
✔ Linting passed

This requires you to either:

  • Have the required lint tools installed on your computer.
  • A working Docker installation, in which case an image with these tools pre-installed is used.

To execute documentation link tests locally:

  1. Navigate to the gitlab-docs directory.
  2. Run the following commands:

    # Check for broken internal links
    bundle exec nanoc check internal_links
    # Check for broken external links (might take a lot of time to complete).
    # This test is set to be allowed to fail and is run only in the gitlab-docs project CI
    bundle exec nanoc check internal_anchors

The ui-docs-links lint job uses haml-lint to test that all documentation links from UI elements (app/views files, for example) are linking to valid pages and anchors.

To run the ui-docs-links test locally:

  1. Open the gitlab directory in a terminal window.
  2. Run:

    bundle exec haml-lint -i DocumentationLinks

If you receive an error the first time you run this test, run bundle install, which installs the dependencies for GitLab, and try again.

If you don’t want to install all of the dependencies to test the links, you can:

  1. Open the gitlab directory in a terminal window.
  2. Install haml-lint:

    gem install haml_lint
  3. Run:

    haml-lint -i DocumentationLinks

If you manually install haml-lint with this process, it does not update automatically and you should make sure your version matches the version used by GitLab.

Local linters

To help adhere to the documentation style guidelines, and improve the content added to documentation, install documentation linters and integrate them with your code editor.

At GitLab, we mostly use:


markdownlint checks that Markdown syntax follows certain rules, and is used by the docs-lint test.

Our Documentation Style Guide and Markdown Guide elaborate on which choices must be made when selecting Markdown syntax for GitLab documentation. This tool helps catch deviations from those guidelines.

markdownlint configuration is found in the following projects:

This configuration is also used in build pipelines.

You can use markdownlint:


Vale is a grammar, style, and word usage linter for the English language. Vale’s configuration is stored in the .vale.ini file located in the root directory of projects.

Vale supports creating custom tests that extend any of several types of checks, which we store in the .linting/vale/styles/gitlab directory in the documentation directory of projects.

You can find Vale configuration in the following projects:

This configuration is also used in build pipelines, where error-level rules are enforced.

You can use Vale:

Vale result types

Vale returns three types of results: suggestion, warning, and error:

  • Suggestion-level results are writing tips and aren’t displayed in CI job output. Suggestions don’t break CI. See a list of suggestion-level rules.
  • Warning-level results are Style Guide violations, aren’t displayed in CI job output, and should contain clear explanations of how to resolve the warning. Warnings may be technical debt, or can be future error-level test items (after the Technical Writing team completes its cleanup). Warnings don’t break CI. See a list of warning-level rules.
  • Error-level results are Style Guide violations, and should contain clear explanations about how to resolve the error. Errors break CI and are displayed in CI job output. of how to resolve the error. Errors break CI and are displayed in CI job output. See a list of error-level rules.

Install linters

At a minimum, install markdownlint and Vale to match the checks run in build pipelines:

  1. Install markdownlint-cli:

    yarn global add markdownlint-cli

    We recommend installing the version of markdownlint-cli used when building the image:docs-lint-markdown.

  2. Install vale. For example, to install using brew for macOS, run:

    brew install vale

These tools can be integrated with your code editor.

Update linters

It’s important to use linter versions that are the same or newer than those run in CI/CD. This provides access to new features and possible bug fixes.

To match the versions of markdownlint-cli and vale used in the GitLab projects, refer to the versions used when building the image:docs-lint-markdown Docker image containing these tools for CI/CD.

Tool Version Command Additional information
markdownlint-cli Latest yarn global add markdownlint-cli n/a
markdownlint-cli Specific yarn global add markdownlint-cli@0.23.2 The @ indicates a specific version, and this example updates the tool to version 0.23.2.
Vale Latest brew update && brew upgrade vale This command is for macOS only.
Vale Specific n/a Not possible using brew, but can be directly downloaded.

Configure editors

Using linters in your editor is more convenient than having to run the commands from the command line.

To configure markdownlint in your editor, install one of the following as appropriate:

To configure Vale in your editor, install one of the following as appropriate:

We don’t use Vale Server.

Configure pre-push hooks

Git pre-push hooks allow Git users to:

  • Run tests or other processes before pushing a branch.
  • Avoid pushing a branch if failures occur with these tests.

lefthook is a Git hooks manager, making configuring, installing, and removing Git hooks easy.

Configuration for lefthook is available in the lefthook.yml file for the gitlab project.

To set up lefthook for documentation linting, see Pre-push static analysis.

Show subset of Vale alerts

You can set Visual Studio Code to display only a subset of Vale alerts when viewing files:

  1. Go to Preferences > Settings > Extensions > Vale.
  2. In Vale CLI: Min Alert Level, select the minimum alert level you want displayed in files.

To display only a subset of Vale alerts when running Vale from the command line, use the --minAlertLevel flag, which accepts error, warning, or suggestion. Combine it with --config to point to the configuration file within the project, if needed:

vale --config .vale.ini --minAlertLevel error doc/**/*.md

Omit the flag to display all alerts, including suggestion level alerts.

Disable Vale tests

You can disable a specific Vale linting rule or all Vale linting rules for any portion of a document:

  • To disable a specific rule, add a <!-- vale gitlab.rulename = NO --> tag before the text, and a <!-- vale gitlab.rulename = YES --> tag after the text, replacing rulename with the filename of a test in the GitLab styles directory.
  • To disable all Vale linting rules, add a <!-- vale off --> tag before the text, and a <!-- vale on --> tag after the text.

Whenever possible, exclude only the problematic rule and line(s).

For more information, see Vale’s documentation.