1 Tests destroying a context during registration at the point when the "extends" option is retrieved.
3 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
7 PASS caught expected exception "InvalidStateError: Failed to execute 'registerElement' on 'Document': Registration failed for type 'x-a'. The context is no longer valid."
9 PASS successfullyParsed is true