Merge pull request #47 from rakuco/test-as-you-commit

Ask for tests for normative changes in CONTRIBUTING.md

Author: anssiko

CONTRIBUTING.md

@@ -21,3 +21,12 @@ If you added a contributor by mistake, you can remove them in a comment with:
 
 If you are making a pull request on behalf of someone else but you had no part in designing the 
 feature, you can remove yourself with the above syntax.
+
+# Tests
+
+For normative changes, a corresponding
+[web-platform-tests](https://github.com/w3c/web-platform-tests) PR is highly appreciated. Typically,
+both PRs will be merged at the same time. Note that a test change that contradicts the spec should
+not be merged before the corresponding spec change. If testing is not practical, please explain why
+and if appropriate [file a web-platform-tests issue](https://github.com/w3c/web-platform-tests/issues/new)
+to follow up later. Add the `type:untestable` or `type:missing-coverage` label as appropriate.