How to release the port number after every JUnit test in spring boot application?

Question

I have a JUnit test class written in spring boot which contains 3 unit tests:

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
@ContextConfiguration
@DirtiesContext(classMode = ClassMode.AFTER_EACH_TEST_METHOD)
public class AppclaitionTest {

    @BeforeClass
    public static void initialize(){
        System.out.println(">>>>>>>Intialization Part!");
    }

    @Test
    public void test1(){
        System.out.println(">>>>>>>Appcliation Test Started! - Test 1");
        Application.main(new String[]{});
        System.out.println(">>>>>>>Appcliation Test Ended! - Test 1");
    }

    @Test
    public void test2(){
        System.out.println(">>>>>>>Appcliation Test Started! - Test 2");
        Application.main(new String[]{});
        System.out.println(">>>>>>>Appcliation Test Ended! - Test 2");
    }

    @Test
    public void test3(){
        System.out.println(">>>>>>>Appcliation Test Started! - Test 3");
        Application.main(new String[]{});
        System.out.println(">>>>>>>Appcliation Test Ended! - Test 3");
    }

    @AfterClass
    public static void destory(){
        System.out.println(">>>>>>>Destroy Part!");
    }
}

If run after the first test, i am getting below the exception:

java.net.BindException: Address already in use: bind

though the application context released, it is not releasing the port number, hence i'm getting the above exception.

Is there any way that I can close the port number before each unit test?

Answer 1

You should consider starting your Spring Boot application by using the SpringApplication class rather than invoking directly the main(String[] args) method of your Spring Boot application that doesn't provide an API to terminate it.

With the SpringApplication way, you could get a ConfigurableApplicationContext instance that provides a way to terminate the running application.

For example :

ConfigurableApplicationContext context;

@Before
public void setup{
    SpringApplication springApplication = new SpringApplicationBuilder()           
            .sources(Application.class)
            .build();
    context = springApplication.run();
}

@After
public void tearDown(){
    SpringApplication.exit(context);
}

@Test
 public void test1(){         
    // action
       ...
    // assertion
       ...
 }

However, you should be cautious about this way of doing.
Starting the Spring Boot application is a relatively expensive operation.
Executing it for any method of test will make slower the tests execution.
Unit tests should be fast.
Integration tests that are executing on a integration machine may be slower.
You should also consider this problematic.

Answer 2

Use @After and @Before to handle before and after calls for each unit test.