This is a testharness.js-based test.
[FAIL] width: var(prop);
  assert_equals: expected "var(prop)" but got ""
[FAIL] width: var(-prop);
  assert_equals: expected "var(-prop)" but got ""
[FAIL] width: var(--prop 20px);
  assert_equals: expected "var(--prop 20px)" but got ""
[FAIL] width: var(--prop, var(prop));
  assert_equals: expected "var(--prop, var(prop))" but got ""
[FAIL] width: var(--prop, var(-prop));
  assert_equals: expected "var(--prop, var(-prop))" but got ""
[FAIL] width: var(20px);
  assert_equals: expected "var(20px)" but got ""
[FAIL] width: var(var(--prop));
  assert_equals: expected "var(var(--prop))" but got ""
Harness: the test ran to completion.