gecko-dev/remote/doc/Testing.md

Testing
=======

The remote agent has unit- and functional tests located under
`remote/test/{unit,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 xcpshell-test --sequential remote/test/unit/test_Assert.js

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

[xpcshell]: https://developer.mozilla.org/en-US/docs/Mozilla/QA/Writing_xpcshell-based_unit_tests


Browser chrome tests
--------------------

We also have a set of functional [browser chrome] tests located
under _remote/test/browser_:

	% ./mach mochitest remote/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/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.targets;
	  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()`.

[browser chrome]: https://developer.mozilla.org/en-US/docs/Mozilla/Browser_chrome_tests
[headless mode]: https://developer.mozilla.org/en-US/Firefox/Headless_mode
[asynchronous tests]: https://developer.mozilla.org/en-US/docs/Mozilla/Browser_chrome_tests#Test_functions
[CDP client]: https://github.com/cyrus-and/chrome-remote-interface


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.

These tests are vendored under _remote/test/puppeteer/_ and are
run locally like this:

	% ./mach test remote/test/puppeteer/test

On try they appear under the `remote(pup)` symbol, but because they’re
a Tier-3 class test job they’re not automatically scheduled.
To schedule the tests, look for `source-test-remote-puppeteer` in
`./mach try fuzzy`.

The tests are written in the behaviour-driven testing framework
[Mocha], which doesn’t support selecting tests by file path like
other harnesses.  It does however come with a myriad of flags to
narrow down the selection a bit: some of the most useful ones include
[`--grep`], [`--ignore`], and [`--file`].

Perhaps the most useful trick is to rename the `describe()` or
`it()` functions to `fdescribe()` and `fit()`, respectively, in
order to run a specific subset of tests.  This does however force
you to edit the test files manually.

A real-world example:

```diff
diff --git a/remote/test/puppeteer/test/frame.spec.js b/remote/test/puppeteer/test/frame.spec.js
index 58e57934a7b8..0531d49d7a12 100644
--- a/remote/test/puppeteer/test/frame.spec.js
+++ b/remote/test/puppeteer/test/frame.spec.js
@@ -48,7 +48,7 @@ module.exports.addTests = function({testRunner, expect}) {
     });
   });

-  describe('Frame.evaluateHandle', function() {
+  fdescribe('Frame.evaluateHandle', function() {
     it('should work', async({page, server}) => {
       await page.goto(server.EMPTY_PAGE);
       const mainFrame = page.mainFrame();
@@ -58,7 +58,7 @@ module.exports.addTests = function({testRunner, expect}) {
   });

   describe('Frame.evaluate', function() {
-    it('should throw for detached frames', async({page, server}) => {
+    fit('should throw for detached frames', async({page, server}) => {
       const frame1 = await utils.attachFrame(page, 'frame1', server.EMPTY_PAGE);
       await utils.detachFrame(page, 'frame1');
       let error = null;
```

[Puppeteer test suite]: https://github.com/GoogleChrome/puppeteer/tree/master/test
[track progress]: https://docs.google.com/spreadsheets/d/1GZ4yO2-NGD6kbsT7aMlUPUpUqTaASpqNxJGKhOQ-_BM/edit#gid=0
[Puppeteer support]: https://bugzilla.mozilla.org/show_bug.cgi?id=puppeteer
[Mocha]: https://mochajs.org/
[`--grep`]: https://mochajs.org/#-grep-regexp-g-regexp
[`--ignore`]: https://mochajs.org/#-ignore-filedirectoryglob
[`--file`]: https://mochajs.org/#-file-filedirectoryglob