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

./wpt 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 either fix all lint errors, or you must whitelist test files to suppress the errors.

Fixing lint errors

You must fix any errors the lint tool reports, unless an error is for something essential to a certain test or that for some other exceptional reason shouldn’t prevent the test from being merged; in those cases you can whitelist test files to suppress the errors. In all other cases, follow the instructions below to fix all errors reported.

  • CONSOLE: Test-file line has a console.*(...) call; fix: remove the console.*(...) call (and in some cases, consider adding an assert_* of some kind in place of it).

  • CR AT EOL: Test-file line ends with CR (U+000D) character; fix: reformat file so each line just has LF (U+000A) line ending (standard, cross-platform “Unix” line endings instead of, e.g., DOS line endings).

  • EARLY-TESTHARNESSREPORT: Test file has an instance of <script src='/resources/testharnessreport.js'> prior to <script src='/resources/testharness.js'>; fix: flip the order.

  • GENERATE_TESTS: Test file line has a generate_tests call; fix: remove the call and call test() a number of times instead.

  • INDENT TABS: Test-file line starts with one or more tab characters; fix: use spaces to replace any tab characters at beginning of lines.

  • INVALID-TIMEOUT: Test file with <meta name='timeout'...> element that has a content attribute whose value is not long; fix: replace the value of the content attribute with long.

  • LATE-TIMEOUT: Test file with <meta name="timeout"...> element after <script src='/resources/testharnessreport.js'> element ; fix: move the <meta name="timeout"...> element to precede the script element.

  • LAYOUTTESTS APIS: Test file uses eventSender, testRunner, or window.internals which are LayoutTests-specific APIs used in WebKit/Blink.

  • MALFORMED-VARIANT: Test file with a <meta name='variant'...> element whose content attribute has a malformed value; fix: ensure the value of the content attribute starts with ? or # or is empty.

  • MISSING-TESTHARNESSREPORT: Test file is missing an instance of <script src='/resources/testharnessreport.js'>; fix: ensure each test file contains <script src='/resources/testharnessreport.js'>.

  • MULTIPLE-TESTHARNESS: Test file with multiple instances of <script src='/resources/testharness.js'>; fix: ensure each test has only one <script src='/resources/testharness.js'> instance.

  • MULTIPLE-TESTHARNESSREPORT: Test file with multiple instances of <script src='/resources/testharnessreport.js'>; fix: ensure each test has only one <script src='/resources/testharnessreport.js'> instance.

  • MULTIPLE-TIMEOUT: Test file with multiple <meta name="timeout"...> elements; fix: ensure each test file has only one instance of a <meta name="timeout"...> element.

  • PARSE-FAILED: Test file failed parsing by manifest builder; fix: examine the file to find the causes of any parse errors, and fix them.

  • PATH LENGTH: Test file’s pathname has a total length greater than 150 characters; fix: use shorter filename to rename the test file.

  • PRINT STATEMENT: A server-side python support file contains a print statement; fix: remove the print statement or replace it with something else that achieves the intended effect (e.g., a logging call).

  • SET TIMEOUT: Test-file line has setTimeout(...) call; fix: replace all setTimeout(...) calls with step_timeout(...) calls.

  • TRAILING WHITESPACE: Test-file line has trailing whitespace; fix: remove trailing whitespace from all lines in the file.

  • VARIANT-MISSING: Test file with a <meta name='variant'...> element that’s missing a content attribute; fix: add a content attribute with an appropriate value to the <meta name='variant'...> element.

  • W3C-TEST.ORG: Test-file line has the string w3c-test.org; fix: either replace the w3c-test.org string with the expression : or a generic hostname like example.org.

Updating the whitelist

Normally you must fix all lint errors. But in the unusual case of error reports for things essential to certain tests or that for other exceptional reasons shouldn’t prevent a merge of a test, you can update and commit the lint.whitelist file in the web-platform-tests root directory to suppress errors the lint tool would report for a test file.

To add a test file or directory to the whitelist, use the following format:

ERROR TYPE:file/name/pattern

For example, to whitelist the file example/file.html such that all TRAILING WHITESPACE errors the lint tool would report for it are suppressed, add the following line to the lint.whitelist file:

TRAILING WHITESPACE:example/file.html

To whitelist an entire directory rather than just one file, use the * wildcard. For example, to whitelist the example directory such that all TRAILING WHITESPACE errors the lint tool would report for any files in it are suppressed, add the following line to the lint.whitelist file:

TRAILING WHITESPACE:example/*

Similarly, you can also use shell-style wildcards to express other filename patterns or directory-name patterns.

Finally, to whitelist just one line in a file, use the following format:

ERROR TYPE:file/name/pattern:line_number

For example, to whitelist just line 128 of the file example/file.html such that any TRAILING WHITESPACE error the lint tool would report for that line is suppressed, add the following to the lint.whitelist file:

TRAILING WHITESPACE:example/file.html:128