We will write a simple unit test to test this repository. The code for the unit test is as follows:

@DataMongoTest
@RunWith(SpringRunner.class)
public class PersonMongoDbRepositoryTest {

      @Autowired
      PersonMongoDbRepository personRepository;

      @Test
      public void simpleTest(){

        personRepository.deleteAll();

        personRepository.save(new Person( "name1"));
        personRepository.save(new Person( "name2"));

        for (Person person : personRepository.findAll()) {
           System.out.println("Person 1: " + person);
        }

        System.out.println("Person 2: " + personRepository.findByName("name1"));

        System.out.println("Person Count: "personRepository.count());
 }

}

Some important things to note are as follows:

• Make sure that MongoDB is running when you run the test.
• @DataMongoTest: The DataMongoTest annotation is used in combination with SpringRunner for a typical MongoDB unit test. This disables auto-configuration for everything except things that are related to MongoDB.
• @Autowired PersonMongoDbRepository personRepository: Autowires the MongoDB repository in order for it to be tested.

We saw that code for interacting with a big database such as MongoDB is made simple, and is very similar to how we talk with a relational database. That's the magic of Spring Data.