emberjs/ember.js — comment on commit 03b685fbbf728c07c6c91e404877073a7aad3ac9
File: packages/ember-views/tests/views/view/attribute_bindings_test.js line 142
By jbrown:

@wagenet I guess this is less expensive as long as you don't need to test DOM interaction? There are probably a bunch of tests that don't really need to append and could use this approach instead. If you set foo to something else, does it update the element even though it's not in the DOM?