SimplePOJO pojo = new SimplePOJO();
pojo.setAnIntegerField(42);
DBObject document = converter.from(pojo).toDocument();
assertThat(document.containsField("an_integer_field"), is(true));
assertThat(document.containsField("_id"), is(true));
assertThat(document.containsField("a_field"), is(false));
assertThat(document.containsField("another_field"), is(false));
assertThat(document.containsField("a_long_field"), is(false));
assertThat(document.containsField("a_double_field"), is(false));