Selenium atoms

Marionette uses a small list of Selenium atoms to interact with web elements. Initially those have been added to ensure a better reliability due to a wider usage inside the Selenium project. But by adding full support for the WebDriver specification they will be removed step by step.

Currently the following atoms are in use:

  • getElementText

  • isElementDisplayed

To use one of those atoms Javascript modules will have to import atom.sys.mjs.

Update required Selenium atoms

In regular intervals the atoms, which are still in use, have to be updated. Therefore they have to be exported from the Selenium repository first, and then updated in atom.sys.mjs.

Export Selenium Atoms

The canonical GitHub repository for Selenium is

https://github.com/SeleniumHQ/selenium.git

so make sure to have an up-to-date local copy of it. If you have to clone it first, it is recommended to specify the --depth=1 argument, so only the last changeset is getting downloaded (which itself might already be more than 100 MB).

git clone --depth=1 https://github.com/SeleniumHQ/selenium.git

To export the correct version of the atoms identify the changeset id (SHA1) of the Selenium repository in the index section of the WebDriver specification.

Fetch that changeset and check it out:

git fetch --depth=1 origin SHA1
git checkout SHA1

Now you can export all the required atoms by running the following commands. Make sure to install bazelisk first.

bazel build //javascript/atoms/fragments:get-text
bazel build //javascript/atoms/fragments:is-displayed

For each of the exported atoms a file can now be found in the folder bazel-bin/javascript/atoms/fragments/. They contain all the code including dependencies for the atom wrapped into a single function.

Update atom.sys.mjs

To update the atoms for Marionette the atoms.js file has to be edited. For each atom to be updated the steps as laid out below have to be performed:

  1. Open the Javascript file of the exported atom. See above for its location.

  2. Add the related function name and element as parameters to the wrapper function, which can be found at the very beginning of the file so that it is equal to the parameters in atom.sys.mjs.

  3. Copy and paste the whole contents of the file into the left textarea on https://jsonformatter.org/json-stringify-online to get a stringified version of all the required functions.

  4. Copy and paste the whole contents of the right textarea, and replace the existing code for the atom in atom.sys.mjs.

Test the changes

To ensure that the update of the atoms doesn’t cause a regression a try build should be run including Marionette unit tests, Firefox ui tests, and all the web-platform-tests.