The Web Platform Tests Project is a W3C-coordinated attempt to build a cross-browser testsuite for the Web-platform stack. However, for mainly historic reasons, the CSS WG testsuite is in a separate repository, csswg-test. Writing tests in a way that allows them to be run in all browsers gives browser projects confidence that they are shipping software that is compatible with other implementations, and that later implementations will be compatible with their implementations. This in turn gives Web authors/developers confidence that they can actually rely on the Web platform to deliver on the promise of working across browsers and devices without needing extra layers of abstraction to paper over the gaps left by specification editors and implementors.

The tests are designed to be run from your local computer. The test environment requires Python 2.7+ (but not Python 3.x). You will also need a copy of OpenSSL. Users on Windows should read the Windows Notes section below.

To get the tests running, you need to set up the test domains in your hosts file. The following entries are required:

127.0.0.1	web-platform.test
127.0.0.1	www.web-platform.test
127.0.0.1	www1.web-platform.test
127.0.0.1	www2.web-platform.test
127.0.0.1	xn--n8j6ds53lwwkrqhv28a.web-platform.test
127.0.0.1	xn--lve-6lad.web-platform.test

Because web-platform-tests uses git submodules, you must ensure that these are up to date. In the root of your checkout, run:

git submodule update --init --recursive

The test environment can then be started using

./serve

This will start HTTP servers on two ports and a websockets server on one port. By default one web server starts on port 8000 and the other ports are randomly-chosen free ports. Tests must be loaded from the first HTTP server in the output. To change the ports, edit the config.json file, for example, replacing the part that reads:

"http": [8000, "auto"]

to some port of your choice e.g.

"http":[1234, "auto"]

If you installed OpenSSL in such a way that running openssl at a command line doesn't work, you also need to adjust the path to the OpenSSL binary. This can be done by adding a section to config.json like:

"ssl": {"openssl": {"binary": "/path/to/openssl"}}

Running wptserve with SSL enabled on Windows typically requires installing an OpenSSL distribution. Shining Light provide a convenient installer that is known to work, but requires a little extra setup.

After installation ensure that the path to OpenSSL is on your %Path% environment variable.

Then set the path to the default OpenSSL configuration file (usually something like C:\OpenSSL-Win32\bin\openssl.cfg in the server configuration. To do this copy config.default.json in the web-platform-tests root to config.json. Then edit the JSON so that the key ssl/openssl/base_conf_path has a value that is the path to the OpenSSL config file.

There is a test runner that is designed to provide a convenient way to run the web-platform tests in-browser. It will run testharness.js tests automatically but requires manual work for reftests and manual tests.

The runner can be found at /tools/runner/index.html on the local server i.e.

https://web-platform.test:8000/tools/runner/index.html

in the default configuration. The first time you use this it has to generate a manifest of all tests. This may take some time, so please be patient.

The master branch is automatically synced to https://w3c-test.org/.

Pull requests that have been checked are automatically mirrored to https://w3c-test.org/submissions/.

Each top-level directory represents a W3C specification: the name matches the shortname used after the canonical address of the said specification under https://www.w3.org/TR/ .

For some of the specifications, the tree under the top-level directory represents the sections of the respective documents, using the section IDs for directory names, with a maximum of three levels deep.

So if you're looking for tests in HTML for "The History interface", they will be under html/browsers/history/the-history-interface/.

Various resources that tests depend on are in common, images, and fonts.

In the vast majority of cases the only upstream branch that you should need to care about is master. If you see other branches in the repository, you can generally safely ignore them.

Save the Web, Write Some Tests!

Absolutely everyone is welcome (and even encouraged) to contribute to test development, so long as you fulfill the contribution requirements detailed in the Contributing Guidelines. No test is too small or too simple, especially if it corresponds to something for which you've noted an interoperability bug in a browser.

The way to contribute is just as usual:

• Fork this repository (and make sure you're still relatively in sync with it if you forked a while ago).
• Create a branch for your changes: git checkout -b topic.
• Make your changes.
• Run the lint script described below.
• Commit locally and push that to your repo.
• Send in a pull request based on the above.

We have a lint tool for catching common mistakes in test files. You can run it manually by starting the lint executable from the root of your local web-platform-tests working directory like this:

./lint

The lint tool is also run automatically for every submitted pull request, and reviewers will not merge branches with tests that have lint errors, so you must fix any errors the lint tool reports. For details on doing that, see the lint-tool documentation.

But in the unusual case of error reports for things essential to a certain test or that for other exceptional reasons shouldn't prevent a merge of a test, update and commit the lint.whitelist file in the web-platform-tests root directory to suppress the error reports. For details on doing that, see the lint-tool documentation.

Sometimes you may want to add a script to the repository that's meant to be used from the command line, not from a browser (e.g., a script for generating test files). If you want to ensure (e.g., for security reasons) that such scripts won't be handled by the HTTP server, but will instead only be usable from the command line, then place them in either:

• the tools subdir at the root of the repository, or

• the tools subdir at the root of any top-level directory in the repository which contains the tests the script is meant to be used with

Any files in those tools directories won't be handled by the HTTP server; instead the server will return a 404 if a user navigates to the URL for a file within them.

If you want to add a script for use with a particular set of tests but there isn't yet any tools subdir at the root of a top-level directory in the repository containing those tests, you can create a tools subdir at the root of that top-level directory and place your scripts there.

For example, if you wanted to add a script for use with tests in the notifications directory, create the notifications/tools subdir and put your script there.

We can sometimes take a little while to go through pull requests because we have to go through all the tests and ensure that they match the specification correctly. But we look at all of them, and take everything that we can.

If you wish to contribute actively, you're very welcome to join the [email protected] mailing list (low traffic) by signing up to our mailing list. The mailing list is archived.

Join us on irc #testing (irc.w3.org, port 6665). The channel is archived.

• How to write and review tests
• Documentation for the wptserve server