This is a testharness.js-based test.
Found 4 FAIL, 0 TIMEOUT, 0 NOTRUN.
[FAIL] e.style['background-image'] = "image-set(url(\\"example.png\\") calc(1dppx * sibling-index()))" should set the property value
  assert_not_equals: property should be set got disallowed value ""
[FAIL] e.style['background-image'] = "-webkit-image-set(url(\\"example.png\\") calc(1dppx * sibling-index()))" should set the property value
  assert_not_equals: property should be set got disallowed value ""
[FAIL] e.style['background-image'] = "image-set(url(\\"example.png\\") calc(1dppx * sign(1em - 10px)))" should set the property value
  assert_not_equals: property should be set got disallowed value ""
[FAIL] e.style['background-image'] = "-webkit-image-set(url(\\"example.png\\") calc(1dppx * sign(1em - 10px)))" should set the property value
  assert_not_equals: property should be set got disallowed value ""
Harness: the test ran to completion.