basic.css

.test-unchanged-properties {
	order: 1;
	background-image: url("img/test.png");
	order: 2;
	background: url(my-img-print.png) top left no-repeat red;
	order: 3;
}

.test-changed-properties {
	order: 1;
	background-image: image-set(
		url(img/test.png) 1x
	);
	order: 2;
	background-image: image-set(
		url(img/test.png) 2x
	);
	order: 3;
	background-image: image-set(
		url(img/test.png) 1x,
		url(img/test-2x.png) 2x
	);
	order: 4;
	background-image: image-set(
		url(img/test.png) 1x,
		url(img/test-2x.png) 2x,
		url(my-img-print.png) 600dpi
	);
	order: 5;
}

.test-mixed-units {
	order: 1;
	background-image: image-set(
		url(img/test.png) 1x,
		url(img/test-2x.png) 2dppx
	);
	order: 2;
	background-image: image-set(
		url(img/test.png) 1x,
		url(img/test-2x.png) 20dpcm
	);
	order: 3;
}

.test-mixed-order {
	order: 1;
	background: image-set(
		url(../images/bck@3x.png) 3x,
		url(../images/bck.png) 1x,
		url(../images/bck@2x.png) 2x
	);
	order: 2;
	background: image-set(
		url(../images/bck@2x.png) 2x,
		url(../images/bck@3x.png) 3x,
		url(../images/bck.png) 1x
	);
	order: 3;
}

.test-no-url {
	order: 1;
	background-image: image-set(
		"img/test.png" 1x,
		"img/test-2x.png" 2x
	);
	order: 2;
	background-image: image-set(
		"img/test.png" 1x,
		"img/test-2x.png" 2x,
		"my-img-print.png" 600dpi
	);
	order: 3;
}

.test-webkit-prefix {
	order: 1;
	background-image: -webkit-image-set(
		url(img/test.png) 1x,
		url(img/test-2x.png) 2x,
		url(my-img-print.png) 600dpi
	);
	order: 2;
}

@media (min-width: 1000px) {
	.test-within-mq-1 {
		background-image: image-set(
			url(img/test.png) 1x,
			url(img/test-2x.png) 2x,
			url(my-img-print.png) 600dpi
		);
	}
}

@media (min-width: 768px) and (max-width: 1024px) {
	.test-within-mq-2 {
		background-image: image-set(
			url(img/test.png) 1x,
			url(img/test-2x.png) 2x,
			url(my-img-print.png) 600dpi
		);
	}
}

.test-unparseable-image-set-function {
	background-image: image-set(url(data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==) 1x, url(img/test-2x.png) 2x);
	background-image: image-set(data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==, url(img/test-2x.png) 2x);
}