Test the setting of the -webkit-image-set function. On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE". Single value for background-image : url(http://www.webkit.org/a) 1x FAIL testComputedStyle("background-image", "-webkit-image-set(url(http://www.webkit.org/a) 1x)") should be -webkit-image-set(url(http://www.webkit.org/a) 1x). Was . Multiple values for background-image : url(http://www.webkit.org/a) 1x, url(http://www.webkit.org/b) 2x FAIL testComputedStyle("background-image", "-webkit-image-set(url(http://www.webkit.org/a) 1x, url(http://www.webkit.org/b) 2x)") should be -webkit-image-set(url(http://www.webkit.org/a) 1x, url(http://www.webkit.org/b) 2x). Was . Multiple values for background-image, out of order : url(http://www.webkit.org/c) 3x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x FAIL testComputedStyle("background-image", "-webkit-image-set(url(http://www.webkit.org/c) 3x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x)") should be -webkit-image-set(url(http://www.webkit.org/c) 3x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x). Was . Duplicate values for background-image : url(http://www.webkit.org/c) 1x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x FAIL testComputedStyle("background-image", "-webkit-image-set(url(http://www.webkit.org/c) 1x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x)") should be -webkit-image-set(url(http://www.webkit.org/c) 1x, url(http://www.webkit.org/b) 2x, url(http://www.webkit.org/a) 1x). Was . Fractional values for background-image : url(http://www.webkit.org/c) 0.2x, url(http://www.webkit.org/b) 2.3x, url(http://www.webkit.org/a) 12.3456x FAIL testComputedStyle("background-image", "-webkit-image-set(url(http://www.webkit.org/c) 0.2x, url(http://www.webkit.org/b) 2.3x, url(http://www.webkit.org/a) 12.3456x)") should be -webkit-image-set(url(http://www.webkit.org/c) 0.2x, url(http://www.webkit.org/b) 2.3x, url(http://www.webkit.org/a) 12.3456x). Was . PASS successfullyParsed is true TEST COMPLETE