This is a testharness.js-based test.
[FAIL] e.style['block-step-insert'] = "margin-box" should set the property value
  assert_not_equals: property should be set got disallowed value ""
[FAIL] e.style['block-step-insert'] = "padding-box" should set the property value
  assert_not_equals: property should be set got disallowed value ""
[FAIL] e.style['block-step-insert'] = "content-box" should set the property value
  assert_not_equals: property should be set got disallowed value ""
Harness: the test ran to completion.