This is a testharness.js-based test.
Harness Error. harness_status.status = 1 , harness_status.message = Uncaught Error: '<position>' is not a valid CSS component
[FAIL] Can set 'background-position' to CSS-wide keywords: initial
assert_equals: expected "CSSKeywordValue" but got "CSSStyleValue"
[FAIL] Can set 'background-position' to CSS-wide keywords: inherit
assert_equals: expected "CSSKeywordValue" but got "CSSStyleValue"
[FAIL] Can set 'background-position' to CSS-wide keywords: unset
assert_equals: expected "CSSKeywordValue" but got "CSSStyleValue"
[FAIL] Can set 'background-position' to CSS-wide keywords: revert
assert_equals: expected "CSSKeywordValue" but got "CSSStyleValue"
[FAIL] Can set 'background-position' to var() references: var(--A)
assert_equals: expected "CSSUnparsedValue" but got "CSSStyleValue"
Harness: the test ran to completion.