Spring: test your MySQL JPA with H2

If in Spring Boot you are using a database you can use for your tests H2 or another similar embedded database.

In our case we are using MySQL / PostgreSQL for production and we want to test our code using @DataJpaTest.

Some relevant information from the documentation:

Annotation for a JPA test that focuses only on JPA components.
Using this annotation will disable full auto-configuration and instead apply only configuration relevant to JPA tests.
By default, tests annotated with @DataJpaTest are transactional and roll back at the end of each test. They also use an embedded in-memory database (replacing any explicit or usually auto-configured DataSource).

Include the DB in the classpath

In our case we use H2, we import the library in Maven

<dependency> 
    <groupId>com.h2database</groupId> 
    <artifactId>h2</artifactId> 
    <scope>test</scope> 
</dependency> 

You have to tell Spring to use the H2 database during the tests, for this you have to create /src/test/resources/application.properties with the connection information for H2

spring.datasource.driver-class-name=org.h2.Driver 
spring.datasource.url=jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1 
spring.datasource.username=sa 
spring.datasource.password=sa 

We create the test class with the required dependencies

import org.junit.jupiter.api.Test; 
import org.junit.runner.RunWith; 
import org.springframework.boot.test.autoconfigure.orm.jpa.DataJpaTest; 
import org.springframework.test.context.junit4.SpringRunner; 
import org.springframework.transaction.annotation.Propagation; 
import org.springframework.transaction.annotation.Transactional; 
 
import static org.assertj.core.api.Assertions.*; 
 
@RunWith(SpringRunner.class) 
@DataJpaTest 
@Transactional(propagation = Propagation.NOT_SUPPORTED) 
class FoodControllerTest { 
 
    @Autowired 
    FoodRepository carbsRepository; 
 
    @Test 
    void createFood() { 
       ... 
       foodRepository.save(carbs); 
       assertThat(foodRepository.count()).isEqualTo(1); 
    }