webidl-attribute-getter-setter-lengths.html

<!DOCTYPE html>
<script src="../resources/testharness.js"></script>
<script src="../resources/testharnessreport.js"></script>
<script>
test(() => {
  let title_descriptor = Object.getOwnPropertyDescriptor(HTMLElement.prototype, 'title');

  // http://heycam.github.io/webidl/#dfn-attribute-getter
  // "The attribute getter is a Function object..."
  // "The value of the Function object’s"length" property is the Number value 0."
  assert_equals(title_descriptor.get.length, 0,
                  "The attribute getter Function object's length property must be 0");

  // http://heycam.github.io/webidl/#dfn-attribute-setter
  // "The attribute setter ... is a Function object..."
  // "The value of the Function object’s "length" property is the Number value 1."
  assert_equals(title_descriptor.set.length, 1,
                  "The attribute setter Function object's length property must be 1");
  }, "Verify WebIDL interface attribute getter/setter function lengths");
</script>

chromium/third_party/blink/web_tests/bindings/webidl-attribute-getter-setter-lengths.html