Application Context is failing to load, as it is not finding any qualifying bean of type EntityManager - spring

Question

While running JUnits, ApplicationContext is not loaded, as it could not find a qualifying bean javax.persistence.EntityManager. However, the application for which the Junit is being written is working. Both the application and JUnits are using the same spring configuration.
My Configuration class looks like below
#Configuration
#EnableTransactionManagement
public class AppConfiguration {
#Autowired private EntityManager entityManager;
#Override #Bean
public CustomRepository<Person> customRepository(){
return new CustomRepository<>(Person.class, entityManager);
}
As you see, I'm able to autowire EntityManager, even though I have not explicitly defined the bean and the application is working without any issues.
Now in my JUnit
#RunWith(SpringRunner.class)
#ContextConfiguration(classes=AppConfiguration.class)
#TestPropertySource(locations = "classpath:application.properties")
public class ControllerTest {
#Autowired
private CController controller;
As you see both application and my Junit are using same configuration. How ever when running JUnit, I'm seeing
Caused by: org.springframework.beans.factory.NoSuchBeanDefinitionException: No qualifying bean of type 'javax.persistence.EntityManager' available: expected at least 1 bean which qualifies as autowire candidate. Dependency annotations: {#org.springframework.beans.factory.annotation.Autowired(required=true)}
I could not understand what in the JUnit is causing the isssue, while the aplication is still working.
Thanks

Answer 1

it clearly means that EntityManager bean is not defined in your application context.
So either you define it by yourself or let Spring-boot do the lifting(Spring-boot auto config your context based on dependencies in your POM file). If you choose the latter option then one option to get rid of the error by adding H2 DB.
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
<scope>runtime</scope>
</dependency>
UPDATE:
In your test, instead of initializing your context using #ContextConfiguration do that with #SpringBootTest it will bootstrap your entire container(including other beans that are not defined in AppConfiguration.java). Read more about in spring-docs