layout/style/test/test_font_face_gc.html

<!DOCTYPE html>
<meta charset=utf-8>
<title>Test for bug 1897589</title>
<script src=/tests/SimpleTest/SimpleTest.js></script>
<link rel=stylesheet type=text/css href=/tests/SimpleTest/test.css>
<script>
function forceGC() {
  SpecialPowers.gc();
  SpecialPowers.forceShrinkingGC();
  SpecialPowers.forceCC();
  SpecialPowers.gc();
  SpecialPowers.forceShrinkingGC();
  SpecialPowers.forceCC();
}
add_task(async function() {
  let face = new FontFace('foo', `url("slow_load.sjs")`);
  let p = face.load();
  // Comment out the following line to fix it.
  face = null;
  forceGC();
  try {
    await p;
    ok(false, "Resolved text/plain request?");
  } catch (ex) {
    ok(true, "Expect rejection due to wrong content-type");
  }
})
</script>