The remote agent has unit- and functional tests located under different folders:

  • Shared Modules: remote/shared/test/xpcshell

  • CDP: remote/cdp/test/{xpcshell,browser}.

You may run all the tests under a particular subfolder like this:

% ./mach test remote

Unit tests

Because tests are run in parallel and xpcshell itself is quite chatty, it can sometimes be useful to run the tests in sequence:

% ./mach xpcshell-test --sequential remote/cdp/test/unit/test_DomainCache.js

The unit tests will appear as part of the X (for xpcshell) jobs on Treeherder.

Browser chrome tests

We also have a set of functional browser chrome tests for CDP located under remote/cdp/test/browser:

% ./mach mochitest remote/cdp/test/browser/browser_cdp.js

The functional tests will appear under the M (for mochitest) category in the remote jobs on Treeherder.

As the functional tests will sporadically pop up new Firefox application windows, a helpful tip is to run them in headless mode:

% ./mach mochitest --headless remote/cdp/test/browser

The --headless flag is equivalent to setting the MOZ_HEADLESS environment variable. You can additionally use MOZ_HEADLESS_WIDTH and MOZ_HEADLESS_HEIGHT to control the dimensions of the virtual display.

The add_task() function used for writing asynchronous tests is replaced to provide some additional test setup and teardown useful for writing tests against the remote agent and the targets.

Before the task is run, the nsIRemoteAgent listener is started and a CDP client is connected. You will use this CDP client for interacting with the agent just as any other CDP client would.

Also target discovery is getting enabled, which means that targetCreated, targetDestroyed, and targetInfoChanged events will be received by the client.

The task function you provide in your test will be called with the three arguments client, CDP, and tab:

  • client is the connection to the nsIRemoteAgent listener, and it provides the a client CDP API

  • CDP is the CDP client class

  • tab is a fresh tab opened for each new test, and is automatically removed after the test has run

This is what it looks like all put together:

add_task(async function testName({client, CDP, tab}) {
  // test tab is implicitly created for us
  info("Current URL: " + tab.linkedBrowser.currentURI.spec);

  // manually connect to a specific target
  const { mainProcessTarget } = RemoteAgent.targetList;
  const target = mainProcessTarget.wsDebuggerURL;
  const client = await CDP({ target });

  // retrieve the Browser domain, and call getVersion() on it
  const { Browser } = client;
  const version = await Browser.getVersion();

       await client.close();

  // tab is implicitly removed

You can control the tab creation behaviour with the createTab option to add_task(taskFunction, options):

add_task(async function testName({client}) {
  // tab is not implicitly created
}, { createTab: false });

If you want to write an asynchronous test without this implicit setup you may instead use add_plain_task(), which works exactly like the original add_task().

Puppeteer tests

In addition to our own Firefox-specific tests, we run the upstream Puppeteer test suite against our implementation to track progress towards achieving full Puppeteer support in Firefox. The tests are written in the behaviour-driven testing framework Mocha.

Check the upstream Puppeteer test suite documentation for instructions on how to skip tests, run only one test or a subsuite of tests.

Puppeteer tests are vendored under remote/test/puppeteer/ and are run locally like this:

% ./mach puppeteer-test

You can also run them against Chrome as:

% ./mach puppeteer-test –product=chrome –subset

--subset disables a check for missing or skipped tests in our log parsing. This check is typically not relevant when running against Chrome.

To schedule the tests on try, look for source-test-remote-puppeteer in ./mach try fuzzy. On try they appear under the remote(pup) symbol.

Test expectation metadata is collected in remote/test/puppeteer-expected.json via log parsing and a custom Mocha reporter under remote/test/puppeteer/json-mocha-reporter.js