public int size() {
    return members.size();
  }
@Test
  public void testSize() {
    JsonObject o = new JsonObject();
    assertThat(o.size()).isEqualTo(0);

    o.add("Hello", new JsonPrimitive(1));
    assertThat(o.size()).isEqualTo(1);

    o.add("Hi", new JsonPrimitive(1));
    assertThat(o.size()).isEqualTo(2);

    o.remove("Hello");
    assertThat(o.size()).isEqualTo(1);
  }