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tests/wpt/web-platform-tests/docs/appendix/reverting.md

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+# Reverting Changes
+
+Testing is imperfect and from time to time changes are merged into master which
+break things for users of web-platform-tests. Such breakage can include:
+
+  * Failures in Travis or Taskcluster runs for this repository, either on the
+    master branch or on pull requests following the breaking change.
+
+  * Breakage in browser engine repositories which import and run
+    web-platform-tests, such as Chromium, Edge, Gecko, Servo and WebKit.
+
+  * Breakage in results collections systems for results dashboards, such as
+    [wpt.fyi](https://wpt.fyi).
+
+  * Breakage in supplemental tooling used by working groups, such as the
+    [CSS build system][].
+
+When such breakage happens, if the maintainers of the affected systems request
+it, pull requests to revert the original change should normally be approved and
+merged as soon as possible. (When the original change itself was fixing a
+serious problem, it's a judgement call, but prefer the fastest path to a stable
+state acceptable to everyone.)
+
+Once a revert has happened, the maintainers of the affected systems are
+expected to work with the original patch author to resolve the problem so that
+the change can be relanded. A reasonable timeframe to do so is within one week.
+
+[CSS build system]: https://github.com/web-platform-tests/wpt/tree/master/css/tools