css/css-images/empty-background-image.html

<!doctype html>
<title>Empty url shouldn't try to load a subresource.</title>
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<link rel="help" href="https://drafts.csswg.org/css-values-4/#url-empty">
<link rel="help" href="https://bugzilla.mozilla.org/show_bug.cgi?id=1302991">
<style>
@import url();
@import url('');
@import url("");
</style>
<div style="background-image: url()"></div>
<div style="background-image: url('')"></div>
<div style='background-image: url("")'></div>
<script>
let t = async_test("Empty url shouldn't try to load a subresource.");
onload = t.step_func_done(function() {
  for (let entry of performance.getEntriesByType("resource")) {
    assert_not_equals(entry.name, location.href, "Shouldn't have tried to request ourselves as a subresource")
  }
});
</script>