mValue("fail");
        input.i.setFormValue(null);
        const formData = new FormData(document.getElementById("form-null"));
        assert_false(formData.has("input-null"));
      }, "ElementInternals.setFormValue(null) clears submission value");

      test(() => {
        const input = document.getElementById("input-undefined");
        input.i.setFormValue("fail");
        input.i.setFormValue(undefined);
        const formData = new FormData(document.getElementById("form-undefined"));
        asser