# testharness.js Tests
```eval_rst
.. toctree::
:maxdepth: 1
idlharness
testharness-api
testdriver-tutorial
testdriver
```
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](server-features) for advanced testing features that are commonly used
with testharness.js. See also the [general guidelines](general-guidelines) for all test types.
## Variants
A test file can have multiple variants by including `meta` elements,
for example:
```html
```
The test can then do different things based on the URL.
There are two utility scripts in that work well together with variants,
`/common/subset-tests.js` and `/common/subset-tests-by-key.js`, where
a test that would otherwise have too many tests to be useful can be
split up in ranges of subtests. For example:
```html
Testing variants
```
With `subsetTestByKey`, the key is given as the first argument, and the
query string can include or exclude a key (will be matched as a regular
expression).
```html
Testing variants by key
```
## 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:
```js
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:
```js
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 at x.any.html
* `dedicatedworker` (default): to be run at x.any.worker.html
* `serviceworker`: to be run at x.any.serviceworker.html (`.https` is implied)
* `sharedworker`: to be run at x.any.sharedworker.html
* `jsshell`: to be run in a JavaScript shell, without access to the DOM
(currently only supported in SpiderMonkey, and skipped in wptrunner)
* `default`: shorthand for the default scopes
* `worker`: 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()
### Specifying a test title in auto-generated boilerplate tests
Use `// META: title=This is the title of the test` at the beginning of the resource.
### 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](#variants) in auto-generated boilerplate tests
Use `// META: variant=url-suffix` at the beginning of the resource. For example,
```
// META: variant=
// META: variant=?wss
```