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| layout | title | order |
|---|---|---|
| page | testharness.js Tests | 4 |
testharness.js tests are the correct type of test to write in any
situation where you are not specifically interested in the rendering
of a page, and where human interaction isn't required; these tests are
written in JavaScript using a framework called testharness.js. It is
documented in two sections:
-
[testharness.js Documentation][testharness-api] — An introduction to the library and a detailed API reference.
-
[idlharness.js Documentation][idlharness] — A library for testing IDL interfaces using
testharness.js.
See [server features][] for advanced testing features that are commonly used with testharness.js. See also the [general guidelines][] for all test types.
Variants
A test file can have multiple variants by including meta elements,
for example:
<meta name="variant" content="">
<meta name="variant" content="?wss">
The test can then do different things based on the URL.
There is a utility script in /common/subset-tests.js that works
well together with variants, where a test that would otherwise have
too many tests to be useful can be split up in ranges of subtests.
For example:
<!doctype html>
<title>Testing variants</title>
<meta name="variant" content="?1-1000">
<meta name="variant" content="?1001-2000">
<meta name="variant" content="?2001-last">
<script src="/resources/testharness.js">
<script src="/resources/testharnessreport.js">
<script src="/common/subset-tests.js">
<script>
const tests = [
{ fn: t => { ... }, name: "..." },
... lots of tests ...
];
for (const test of tests) {
subsetTest(async_test, test.fn, test.name);
}
</script>
Auto-generated test boilerplate
While most JavaScript tests require a certain amount of HTML boilerplate to include the test library, etc., tests which are expressible purely in script (e.g. tests for workers) can have all the needed HTML and script boilerplate auto-generated.
Standalone window tests
Tests that only require a script file running in window scope can use
standalone window tests. In this case the test is a javascript file
with the extension .window.js. This is sourced from a generated
document which sources testharness.js, testharnessreport.js and
the test script. For a source script with the name
example.window.js, the corresponding test resource will be
example.window.html.
Standalone workers tests
Tests that only require assertions in a dedicated worker scope can use
standalone workers tests. In this case, the test is a JavaScript file
with extension .worker.js that imports testharness.js. The test can
then use all the usual APIs, and can be run from the path to the
JavaScript file with the .js removed.
For example, one could write a test for the FileReaderSync API by
creating a FileAPI/FileReaderSync.worker.js as follows:
importScripts("/resources/testharness.js");
test(function () {
var blob = new Blob(["Hello"]);
var fr = new FileReaderSync();
assert_equals(fr.readAsText(blob), "Hello");
}, "FileReaderSync#readAsText.");
done();
This test could then be run from FileAPI/FileReaderSync.worker.html.
Multi-global tests
Tests for features that exist in multiple global scopes can be written in a way
that they are automatically run in several scopes. In this case, the test is a
JavaScript file with extension .any.js, which can use all the usual APIs.
By default, the test runs in a window scope and a dedicated worker scope.
For example, one could write a test for the Blob constructor by
creating a FileAPI/Blob-constructor.any.js as follows:
test(function () {
var blob = new Blob();
assert_equals(blob.size, 0);
assert_equals(blob.type, "");
assert_false(blob.isClosed);
}, "The Blob constructor.");
This test could then be run from FileAPI/Blob-constructor.any.worker.html as well
as FileAPI/Blob-constructor.any.html.
It is possible to customize the set of scopes with a metadata comment, such as
// META: global=sharedworker
// ==> would run in the default window and dedicated worker scopes,
// as well as the shared worker scope
// META: global=!default,serviceworker
// ==> would only run in the service worker scope
// META: global=!window
// ==> would run in the default dedicated worker scope, but not the
// window scope
// META: global=worker
// ==> would run in the default window scope, as well as in the
// dedicated, shared and service worker scopes
For a test file x.any.js, the available scope keywords
are:
window(default): to be run atx.any.htmldedicatedworker(default): to be run atx.any.worker.htmlserviceworker: to be run atx.https.any.serviceworker.htmlsharedworker: to be run atx.any.sharedworker.htmldefault: shorthand for the default scopesworker: shorthand for the dedicated, shared and service worker scopes
To check if your test is run from a window or worker you can use the following two methods that will be made available by the framework:
self.GLOBAL.isWindow()
self.GLOBAL.isWorker()
Including other JavaScript resources in auto-generated boilerplate tests
Use // META: script=link/to/resource.js at the beginning of the resource. For example,
// META: script=/common/utils.js
// META: script=resources/utils.js
can be used to include both the global and a local utils.js in a test.
Specifying a timeout of long in auto-generated boilerplate tests
Use // META: timeout=long at the beginning of the resource.
Specifying test variants in auto-generated boilerplate tests
Use // META: variant=url-suffix at the beginning of the resource. For example,
// META: variant=
// META: variant=?wss
[general guidelines]: {{ site.baseurl }}{% link _writing-tests/general-guidelines.md %} [testharness-api]: {{ site.baseurl }}{% link _writing-tests/testharness-api.md %} [idlharness]: {{ site.baseurl }}{% link _writing-tests/idlharness.md %} [server features]: {{ site.baseurl }}{% link _writing-tests/server-features.md %}