There should be layout tests for Feature Policy which demonstrate the correct enabling and disabling of features in various frame embedding scenarios, with different types of policies at different levels.

A comprehensive test suite will likely involve at least two levels of nesting, with three different origins. We should be able to use 127.0.0.1:8000, 127.0.0.2:8000 and localhost:8000 (127.0.0.1 is same-origin, localhost is used already in cross-origin tests, and hopefully 127.0.0.2 is also bound to the test web server)