This is a testharness.js-based test.
PASS # AUDIT TASK RUNNER STARTED.
PASS Executing "decoding-on-detached-iframe"
PASS Audit report
PASS > [decoding-on-detached-iframe] 
FAIL X decodeAudioData() upon a detached iframe rejected correctly but got NotAllowedError instead of InvalidStateError. Got Promise. assert_true: expected true got false
FAIL < [decoding-on-detached-iframe] 1 out of 1 assertions were failed. assert_true: expected true got false
FAIL # AUDIT TASK RUNNER FINISHED: 1 out of 1 tasks were failed. assert_true: expected true got false
Harness: the test ran to completion.