How to use embedded MongoDB with SpringBoot v2.6.2?

The documentation states:

2.2.4. Embedded Mongo

Spring Boot offers auto-configuration for Embedded Mongo. To use it in your Spring Boot application, add a dependency on de.flapdoodle.embed:de.flapdoodle.embed.mongo and set the spring.mongodb.embedded.version property to match the version of MongoDB that your application will use in production. The default download configuration allows access to most of the versions listed in Embedded Mongo’s Version class as well as some others. Configuring an inaccessible version will result in an error when attempting to download the server. Such an error can be corrected by defining an appropriately configured DownloadConfigBuilderCustomizer bean.

The port that Mongo listens on can be configured by setting the spring.data.mongodb.port property. To use a randomly allocated free port, use a value of 0. The MongoClient created by MongoAutoConfiguration is automatically configured to use the randomly allocated port. If you do not configure a custom port, the embedded support uses a random port (rather than 27017) by default.

If you have SLF4J on the classpath, the output produced by Mongo is automatically routed to a logger named org.springframework.boot.autoconfigure.mongo.embedded.EmbeddedMongo.

You can declare your own IMongodConfig and IRuntimeConfig beans to take control of the Mongo instance’s configuration and logging routing. The download configuration can be customized by declaring a DownloadConfigBuilderCustomizer bean.

Therefore add the below dependency in scope:test if you want it to only be applied for Tests.

    <dependency>
        <groupId>de.flapdoodle.embed</groupId>
        <artifactId>de.flapdoodle.embed.mongo</artifactId>
        <scope>test</scope>
    </dependency>

As well you need to set the version in your application.properties file:

spring.mongodb.embedded.version=4.0.21

https://docs.spring.io/spring-boot/docs/current/reference/html/data.html#data.nosql.mongodb.embedded

Working Example:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.6.2</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example.mongodb.embedded</groupId>
    <artifactId>mongodb-app</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>mongodb-app</name>
    <description>Demo project for usage of embedded mongodb</description>
    <properties>
        <java.version>11</java.version>
    </properties>
    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-data-mongodb</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <version>1.18.16</version>
            <scope>provided</scope>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
        <dependency>
            <groupId>de.flapdoodle.embed</groupId>
            <artifactId>de.flapdoodle.embed.mongo</artifactId>
            <scope>test</scope>
        </dependency>

    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <executions>
                    <execution>
                        <id>integration-test</id>
                        <goals>
                            <goal>test</goal>
                        </goals>
                        <phase>integration-test</phase>
                        <configuration>
                            <excludes>
                                <exclude>none</exclude>
                            </excludes>
                            <includes>
                                <include>**/*IT.java</include>
                            </includes>
                        </configuration>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>

</project>

UserRepository:

public interface UserRepository extends MongoRepository<User, Long> {

    //Spring converts this to Regex findByFirstnameRegex(String firstname)  {"firstname" : {"$regex" : firstname }}
    // automatically
    public List<User> findByFirstName(String firstName);

}

User:

@Data
@Builder
public class User {

    @Id
    private Long id;

    private String firstName;
    private String lastName;

}

Test:

@DataMongoTest
@TestInstance(TestInstance.Lifecycle.PER_CLASS)
public class UserControllerIT {

    @Autowired
    private UserRepository userRepository;

    @BeforeAll
    public void setup(){

        userRepository.save(User.builder().id(1L).firstName("James").lastName("Bond").build());
        userRepository.save(User.builder().id(2L).firstName("James").lastName("Farley").build());
        userRepository.save(User.builder().id(3L).firstName("Marley").lastName("Hemp").build());
        userRepository.save(User.builder().id(4L).firstName("James").lastName("Bond").build());

    }

    @Test
    public void test_getById_successfull() throws Exception {
        Assertions.assertEquals("James", userRepository.findByFirstName("James").get(0).getFirstName());
    }

}

src/test/resources/application.properties

spring.data.mongodb.database=test
spring.data.mongodb.port=27017
spring.mongodb.embedded.version=4.0.2