[java] How to write JUnit test with Spring Autowire?

Here are the files that I use:

component.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
    xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:context="http://www.springframework.org/schema/context"
    xmlns:jee="http://www.springframework.org/schema/jee"
    xsi:schemaLocation="http://www.springframework.org/schema/beans
         http://www.springframework.org/schema/beans/spring-beans-3.0.xsd
         http://www.springframework.org/schema/context
         http://www.springframework.org/schema/context/spring-context-3.0.xsd 
         http://www.springframework.org/schema/jee http://www.springframework.org/schema/jee/spring-jee-3.0.xsd">

    <context:component-scan
        base-package="controllers,services,dao,org.springframework.jndi" />
</beans>

ServiceImpl.java

@org.springframework.stereotype.Service
public class ServiceImpl implements MyService {

    @Autowired
    private MyDAO myDAO;

    public void getData() {...}    
}

ServiceImplTest.java

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration("classpath*:conf/components.xml")
public class ServiceImplTest{

    @Test
    public void testMyFunction() {...}
}

Error:

16:22:48.753 [main] ERROR o.s.test.context.TestContextManager - Caught exception while allowing TestExecutionListener [org.springframework.test.context.support.DependencyInjectionTestExecutionListener@2092dcdb] to prepare test instance [services.ServiceImplTest@9e1be92]
org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'services.ServiceImplTest': Injection of autowired dependencies failed; nested exception is org.springframework.beans.factory.BeanCreationException: Could not autowire field: private services.ServiceImpl services.ServiceImplTest.publishedServiceImpl; nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException: No matching bean of type [services.ServiceImpl] found for dependency: expected at least 1 bean which qualifies as autowire candidate for this dependency. Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}
    at org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor.postProcessPropertyValues(AutowiredAnnotationBeanPostProcessor.java:287) ~[spring-beans.jar:3.1.2.RELEASE]

In Spring 2.1.5 at least, the XML file can be conveniently replaced by annotations. Piggy backing on @Sembrano's answer, I have this. "Look ma, no XML".

It appears I to had list all the classes I need @Autowired in the @ComponentScan

@RunWith(SpringJUnit4ClassRunner.class)
@ComponentScan(
    basePackageClasses = {
            OwnerService.class
            })
@EnableAutoConfiguration
public class OwnerIntegrationTest {
    
    @Autowired
    OwnerService ownerService;
    
    @Test
    public void testOwnerService() {
       Assert.assertNotNull(ownerService);
    }
}

You should make another XML-spring configuration file in your test resource folder or just copy the old one, it looks fine, but if you're trying to start a web context for testing a micro service, just put the following code as your master test class and inherits from that:

@WebAppConfiguration
@RunWith(SpringRunner.class)
@ContextConfiguration(locations = "classpath*:spring-test-config.xml")
public abstract class AbstractRestTest {
    @Autowired
    private WebApplicationContext wac;
}

I think somewhere in your codebase are you @Autowiring the concrete class ServiceImpl where you should be autowiring it's interface (presumably MyService).

A JUnit4 test with Autowired and bean mocking (Mockito):

// JUnit starts spring context
@RunWith(SpringRunner.class)
// spring load context configuration from AppConfig class
@ContextConfiguration(classes = AppConfig.class)
// overriding some properties with test values if you need
@TestPropertySource(properties = {
        "spring.someConfigValue=your-test-value",
})
public class PersonServiceTest {

    @MockBean
    private PersonRepository repository;

    @Autowired
    private PersonService personService; // uses PersonRepository    

    @Test
    public void testSomething() {
        // using Mockito
        when(repository.findByName(any())).thenReturn(Collection.emptyList());
        Person person = new Person();
        person.setName(null);

        // when
        boolean found = personService.checkSomething(person);

        // then
        assertTrue(found, "Something is wrong");
    }
}

I've done it with two annotations for test class: @RunWith(SpringRunner.class) and @SpringBootTest. Example:

@RunWith(SpringRunner.class )
@SpringBootTest
public class ProtocolTransactionServiceTest {

    @Autowired
    private ProtocolTransactionService protocolTransactionService;
}

@SpringBootTest loads the whole context, which was OK in my case.