The course material contains JS code that can break and needs to be checked for functionality. Examples are theme/speaker-notes.js or theme/book.js.

Comprehensive Rust is using webdriverIO and the webdriverIO Expect API in combination with Mocha. WebdriverIO is taking care of accessing the webpage with a real browser and can access the state of the page so behavior can be asserted.

The Static Server Service is used mainly in the CI to serve the book on port localhost:8080 such that the test runner can access it. This mode is used when npm start or npm test is executed.

Tip: Use cargo xtask web-tests to run the tests in this directory from anywhere in the repository.

For local testing and quick iterations it is possible to use cargo xtask serve which creates a small HTTP server on port 3000 by default. There is a special config that is invoked with npm run test-mdbook that uses http://localhost:3000

When you see tests failing they should already indicate what checks broke for specific pages.

You might e.g. need to reduce the length of an overlong page (or get an exemption) or updating some mdbook infrastructure had a breaking change that breaks functionality. These issues need to be fixed before this change is merged.

Sometimes tests can also fail in the CI environment with errors like this.

ERROR webdriver: WebDriverError: tab crashed

If you see messages like these, it may indicate an issue with the web-tests that is not caused by your changes. Please file a bug to report this. As a temporary workaround, if all other checks pass and you are confident your changes are correct, you may override the web-test requirement to merge your pull request.