border-image-slice-shorthand-reset.html

<!DOCTYPE html>
<link rel="help" href="https://drafts.csswg.org/css-backgrounds/#border-image-slice" />
<link rel="help" href="https://drafts.csswg.org/css-backgrounds/#border-image" />
<script src="/resources/testharness.js"></script>
<script src="/resources/testharnessreport.js"></script>
<style>
  div {
    border: 1px solid;
    border-image-slice: 1;
  }
  div {
    /* Should reset border-image-slice */
    border-image: linear-gradient(black, black);
  }
</style>
<div>This text should not have a border, just corner dots</div>
<script>
  test(() => {
    assert_equals(getComputedStyle(document.querySelector("div")).borderImageSlice, "100%");
  }, "Check that the border-image shorthand resets border-image-slice to its initial value.");
</script>

chromium/third_party/blink/web_tests/external/wpt/css/css-backgrounds/border-image-slice-shorthand-reset.html