@Test
 public void testIn() {
   coll.save(new MockObject());
   String id = coll.findOne().id;
   assertThat(
       coll.find().in("_id", id, new org.bson.types.ObjectId().toString()).toArray(), hasSize(1));
 }
 @Test
 public void testSimpleEquals() {
   coll.save(new MockObject());
   String id = coll.findOne().id;
   assertNotNull(coll.findOne(DBQuery.is("_id", id)));
 }