Spring Boot TestEntityManager
last modified July 29, 2023
In this article we show how to use TestEntityManager in JPA tests. TestEntityManager provides a subset of EntityManager methods that are useful for tests as well as helper methods for common testing tasks such as persist or find.
Spring is a popular Java application framework for creating enterprise applications. Spring Boot is an evolution of Spring framework which helps create stand-alone, production-grade Spring based applications with minimal effort.
TestEntityManager
TestEntityManager allows to use EntityManager
in tests. Spring Repository is an abstraction over
EntityManager; it shields developers from lower-level details of
JPA and brings many convenient methods. But Spring allows to use
EntityManager when needed in application code and tests.
In our tests, we can inject a DataSource, @JdbcTemplate, @EntityManager or any Spring Data repository from our application.
Spring TestEntityManager example
The following application uses TestEntityManager to save a few
city entities in a test method.
build.gradle
...
src
├───main
│ ├───java
│ │ └───com
│ │ └───zetcode
│ │ │ Application.java
│ │ │ MyRunner.java
│ │ ├───model
│ │ │ City.java
│ │ └───repository
│ │ CityRepository.java
│ └───resources
└───test
└───java
└───com
└───zetcode
└───repository
CityRepositoryTest.java
This is the project structure.
plugins {
id 'org.springframework.boot' version '3.1.1'
id 'io.spring.dependency-management' version '1.1.0'
id 'java'
}
group = 'com.example'
version = '0.0.1-SNAPSHOT'
sourceCompatibility = '17'
repositories {
mavenCentral()
}
dependencies {
implementation 'org.springframework.boot:spring-boot-starter-data-jpa'
testImplementation 'org.springframework.boot:spring-boot-starter-test'
runtimeOnly 'com.h2database:h2'
}
test {
useJUnitPlatform()
}
The Gradle build file contains dependencies for Spring Data JPA, testing, and H2 database.
package com.zetcode.model;
import jakarta.persistence.Entity;
import jakarta.persistence.GeneratedValue;
import jakarta.persistence.GenerationType;
import jakarta.persistence.Id;
import jakarta.persistence.Table;
import java.util.Objects;
@Entity
@Table(name = "cities")
public class City {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
private Long id;
private String name;
private int population;
public City() {
}
public City(String name, int population) {
this.name = name;
this.population = population;
}
public Long getId() {
return id;
}
public void setId(Long id) {
this.id = id;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public int getPopulation() {
return population;
}
public void setPopulation(int population) {
this.population = population;
}
@Override
public int hashCode() {
int hash = 7;
hash = 79 * hash + Objects.hashCode(this.id);
hash = 79 * hash + Objects.hashCode(this.name);
hash = 79 * hash + this.population;
return hash;
}
@Override
public boolean equals(Object obj) {
if (this == obj) {
return true;
}
if (obj == null) {
return false;
}
if (getClass() != obj.getClass()) {
return false;
}
final City other = (City) obj;
if (this.population != other.population) {
return false;
}
if (!Objects.equals(this.name, other.name)) {
return false;
}
return Objects.equals(this.id, other.id);
}
@Override
public String toString() {
var builder = new StringBuilder();
builder.append("City{id=").append(id).append(", name=")
.append(name).append(", population=")
.append(population).append("}");
return builder.toString();
}
}
This is the City entity.
package com.zetcode.repository;
import com.zetcode.model.City;
import org.springframework.data.repository.CrudRepository;
import org.springframework.stereotype.Repository;
import java.util.List;
@Repository
public interface CityRepository extends CrudRepository<City, Long> {
List<City> findByName(String name);
}
CityRepository contains the custom findByName
method. Spring inspects the name of the method and derives a query from its
keywords.
package com.zetcode;
import com.zetcode.model.City;
import com.zetcode.repository.CityRepository;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.CommandLineRunner;
import org.springframework.stereotype.Component;
@Component
public class MyRunner implements CommandLineRunner {
private static final Logger logger = LoggerFactory.getLogger(MyRunner.class);
private final CityRepository cityRepository;
@Autowired
public MyRunner(CityRepository cityRepository) {
this.cityRepository = cityRepository;
}
@Override
public void run(String... args) throws Exception {
logger.info("Saving cities");
cityRepository.save(new City("Bratislava", 432000));
cityRepository.save(new City("Budapest", 1759000));
cityRepository.save(new City("Prague", 1280000));
cityRepository.save(new City("Warsaw", 1748000));
logger.info("Retrieving cities");
var cities = cityRepository.findAll();
cities.forEach(city -> logger.info("{}", city));
}
}
In MyRunner we use the CityRepository to save and
retrieve entities. The data is stored in the in-memory H2 database.
package com.zetcode;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
@SpringBootApplication
public class Application {
public static void main(String[] args) {
SpringApplication.run(Application.class, args);
}
}
The Application sets up the Spring Boot application.
The @SpringBootApplication enables auto-configuration and
component scanning.
package com.zetcode.repository;
import com.zetcode.model.City;
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest;
import org.springframework.boot.test.autoconfigure.orm.jpa.TestEntityManager;
import static org.assertj.core.api.Assertions.assertThat;
import static org.junit.jupiter.api.Assertions.assertEquals;
@DataJpaTest
public class CityRepositoryTest {
@Autowired
private TestEntityManager entityManager;
@Autowired
private CityRepository repository;
@Test
public void testFindByName() {
entityManager.persist(new City("Bratislava", 432000));
entityManager.persist(new City("Budapest", 1759000));
entityManager.persist(new City("Prague", 1280000));
entityManager.persist(new City("Warsaw", 1748000));
var cities = repository.findByName("Bratislava");
assertEquals(1, cities.size());
assertThat(cities).extracting(City::getName).containsOnly("Bratislava");
}
}
In CityRepositoryTest, we test the custom JPA method.
@Autowired private TestEntityManager entityManager;
We inject the TestEntityManager.
@DataJpaTest
public class CityRepositoryTest {
@DataJpaTest is used to test JPA repositories. The annotation
disables full auto-configuration and applies only configuration relevant to JPA
tests. By default, tests annotated with @DataJpaTest use an embedded in-memory
database.
entityManager.persist(new City("Bratislava", 432000));
entityManager.persist(new City("Budapest", 1759000));
entityManager.persist(new City("Prague", 1280000));
entityManager.persist(new City("Warsaw", 1748000));
We save four cities with EntityManager's persist
method.
var cities = repository.findByName("Bratislava");
assertEquals(1, cities.size());
We test that the findByName method returns one city.
assertThat(cities).extracting(City::getName).containsOnly("Bratislava");
Here we test the name of the city.
$ ./gradlew test
We run the tests.
In this article we have used TestEntityManager in our tests.