Unit testing with JUnit 4 using Spring's application context

JUnit tests are run outside Spring; Spring is not initialized before the tests are run. To be able to use the beans defined in the configuration files and dependency injection, some bootstrapping code needs to be added to the test class.

How to do it…

Follow these steps to test a method using the Spring's application context with JUnit 4:

1. Add the spring-test Maven dependency in pom.xml:

   <dependency>
     <groupId>org.springframework</groupId>
     <artifactId>spring-test</artifactId>
     <version>4.1.1.RELEASE</version>
     <scope>test</scope>
   </dependency>

2. Add these annotations to the test class:

   @RunWith(SpringJUnit4ClassRunner.class)
   @ContextConfiguration(classes = {AppConfig.class})
   @WebAppConfiguration
   public class TestControllerTest {
   …

3. Use Spring beans as usual, for example, as @Autowired fields:

   @Autowired
   private UserDAO userDAO;
   
   @Test
   public void testListUsers() {
     List<User...