tor-browser

This directory contains tests for the Compute Pressure specification.

How to write tests

Tests that only need to run on a window

To test this API, one needs to be able to control the pressure data that will be reported to script. At a high level, this is done by calling certain WebDriver endpoints via their corresponding testdriver wrappers.

Tests that need to run on windows and dedicated workers

Certain [testdriver limitations](https://web-platform-tests.org/writing-tests/testdriver.html#using-test-driver-in-other-browsing-contexts) require calls to be made from the top-level test context, which effectively prevents us from simply [running the same test from multiple globals with any.js](https://web-platform-tests.org/writing-tests/testharness.html#tests-for-other-or-multiple-globals-any-js).

What we do instead is [write all tests for the Window global](https://web-platform-tests.org/writing-tests/testharness.html#window-tests), use variants for specifying different globals and using the pressure_test() and mark_as_done() helpers.

In short, the boilerplate for a new test foo.https.window.js looks like this:

// META: variant=?globalScope=window
// META: variant=?globalScope=dedicated_worker
// META: script=/resources/testdriver.js
// META: script=/resources/testdriver-vendor.js
// META: script=/common/utils.js
// META: script=/common/dispatcher/dispatcher.js
// META: script=./resources/common.js

pressure_test(async t => {
}, 'my test');

mark_as_done();

• The variants specify which global context the tests should run on. The only

two options are window and dedicated_worker.

• We need to include all those scripts for the testdriver and

RemoteContext infrastructure to work.

• pressure_test() is a wrapper around a promise_test() that takes care of

running the test either in the current context (when globalScope=window) or in a dedicated worker via RemoteContext and fetch_tests_from_worker() (when globalScope=dedicated_worker).

• mark_as_done() is a no-op when globalScope=window, but is necessary when

globalScope=dedicated_worker to ensure that all tests have run and that `done()` is called in the worker context.

Shared workers

Since custom pressure states are stored in a top-level navigables, they are currently not integrated with shared workers (see [spec issue 285](https://github.com/w3c/compute-pressure/issues/285)) and support for testing shared workers is limited.