Using chromote in CRAN tests

We do recommend that you test your package’s integration with chromote, just not on CRAN. Instead, use a continuous testing service, like GitHub Actions, and include testthat::skip_on_cran() in tests that require Chrome or chromote.

There are a number of issues with testing package functionality based on chromote on CRAN:

• By default, chromote uses the system installation of Chrome, which can change frequently and without warning.

• chromote’s API depends entirely on Chrome, which may change or break between releases.

• There is no 100% reliable way to check or test which system-installed version of Chrome is used on CRAN. While chromote_info() can generally provide this information, we use heuristics to gather the Chrome version that do not always work.

• While chromote now provides features to download and use any version of Chrome, these features should not be used on CRAN. For one, downloading Chrome unnecessarily consumes CRAN’s limited resources. Furthermore, testing against a pinned version of Chrome won’t alert you to issues with the latest version.

Given these challenges, we instead recommend:

1. Using testthat::skip_on_cran() for tests that rely on the availability of Chrome.

2. Run tests in a CI environment, ideally on a weekly or monthly schedule.

3. Use the system version of Chrome provided by the CI environment, or use

   local_chrome_version("latest-stable")

   to ensure you’re testing against the latest stable version of Chrome.

   local_chrome_version("latest-stable", binary = "chrome-headless-shell")

   is another valid choice. See vignette("which-chrome") for details.