Testing with JUnit

You can use JUnit to create test cases to validate your JPA mappings.

• Create a JUnit @BeforeAll method that initializes an EntityManagerFactory which we will use to create EntityManager objects.

• Create JUnit @BeforeEach and @AfterEach methods to initialize and close an EntityManager object.

As the names imply, your @BeforeEach method is invoked before each test and your @AfterEach method runs after each test.

Create individual @Test methods to verify your mappings result in values in line with your expectations.

Drill

We are going to create a JUnit test for our Customer entity.

1. In the entities package in src/test/java, create a new JUnit Jupiter test case named CustomerTest.java.

2. Create method stubs for setUpBeforeClass(), tearDownAfterClass, setUp(), and tearDown().

3. Include the JUnit assertion library:

 import static org.junit.jupiter.api.Assertions.*;

1. Add two private fields to the newly created class:

private static EntityManagerFactory emf;
private EntityManager em;

1. Use @BeforeAll and @AfterAll to initialize and close the EntityManagerFactory.

@BeforeAll
static void setUpBeforeClass() throws Exception {
    emf = Persistence.createEntityManagerFactory("VideoStore");
}

@AfterAll
static void tearDownAfterClass() throws Exception {
    emf.close();
}

1. Use @BeforeEach and @AfterEach to initialize and close the EntityManager.

@BeforeEach
void setUp() throws Exception {
    em = emf.createEntityManager();
}

@AfterEach
void tearDown() throws Exception {
    em.close();
}

1. Run the test by right clicking on the test in Eclipse's Project Explorer and choosing Run As -> JUnit Test.

2. If everything is configured correctly, the test should run and the test() stub should cause an AssertionFailedError.

3. If you get a PersistenceException or some other error, check your persistence unit name and other configuration and resolve the issue before continuing.

4. Write tests.

5. Change the method test to test_Customer_mappings and remove the fail method. Add code to find the Customer entity with id of 1, and call assertEquals() to verify that each field contains expected values. The expected values are in the customer table in the database, so you will find these values by querying the database via the command line.

1. Run the test and make any changes necessary until it passes.

Practice Exercise

The order in which you close these resources does matter. Closing emf before em would throw an exception. Can you guess why?

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