This is a testharness.js-based test.
FAIL Fetching about:blank (GET) is OK promise_test: Unhandled rejection with value: object "TypeError: Failed to fetch"
FAIL Fetching about:blank (PUT) is OK promise_test: Unhandled rejection with value: object "TypeError: Failed to fetch"
FAIL Fetching about:blank (POST) is OK promise_test: Unhandled rejection with value: object "TypeError: Failed to fetch"
PASS Fetching about:invalid.com is KO
PASS Fetching about:config is KO
PASS Fetching about:unicorn is KO
Harness: the test ran to completion.