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 add an exception to suppress the 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 add an exception to suppress the errors. In all other cases, follow the instructions below to fix all errors reported.
.. wpt-lint-rules:: tools.lint.rules
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.ignore 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 list, use the following format:
ERROR TYPE:file/name/pattern
For example, to ignore all TRAILING WHITESPACE errors in the file example/file.html, add the following line to the lint.ignore file:
TRAILING WHITESPACE:example/file.html
To ignore errors for an entire directory rather than just one file, use the * wildcard. For example, to ignore all TRAILING WHITESPACE errors in the example directory, add the following line to the lint.ignore file:
TRAILING WHITESPACE:example/*
Similarly, you can also use shell-style wildcards to express other filename patterns or directory-name patterns.
Finally, to ignore just one line in a file, use the following format:
ERROR TYPE:file/name/pattern:line_number
For example, to ignore the TRAILING WHITESPACE error for just line 128 of the file example/file.html, add the following to the lint.ignore file:
TRAILING WHITESPACE:example/file.html:128