[sibling-function-descriptors.tentative.html]
  [sibling-index() should not be allowed in @font-feature-values descriptors]
    expected: FAIL

  [sibling-count() should not be allowed in @font-feature-values descriptors]
    expected: FAIL

  [sibling-index() should not be allowed in @font-face descriptors]
    expected:
      if (os == "mac") and not debug and (version == "OS X 14.7.5"): [PASS, FAIL]

  [sibling-count() should not be allowed in @font-face descriptors]
    expected:
      if (os == "mac") and not debug and (version == "OS X 14.7.5"): [PASS, FAIL]