This is a testharness.js-based test.
[FAIL] @supports at-rule 1
  assert_equals: expected "at-rule(@supports)" but got "at-rule( @supports)"
[FAIL] @supports at-rule 2
  assert_equals: expected "at-rule(@supports)" but got "at-rule(@supports )"
[FAIL] @supports at-rule 11
  assert_equals: expected "at-rule(@--123)" but got "at-rule(@--\\\\31 23)"
Harness: the test ran to completion.