@Override
    public String toString() {
        return MoreObjects.toStringHelper("Load").add("rate", rate())
                .add("latest", latest()).toString();

    }
@Test
    public void testToString() {
        DefaultLoad load = new DefaultLoad(20, 10);

        String s = load.toString();
        assertThat(s, containsString("Load{rate=1, latest=20}"));
    }