Testing JPA-based applications - JUnit in Action - page 381

public void testDeleteUserWithTelephone() throws Exception {
beginTransaction();
long id = ELFunctionMapperImpl.getId(User. class );
dao.deleteUser(id);
commitTransaction();
}

}
Running these tests will expose the first bug in the DAO implementation, because
testDeleteUserWithTelephone() fails with a constraint violation exception. Although
the user row was deleted, its telephone wasn't. The reason? Cascade deletes are taken
into account only when the EntityManager 's remove() method is called, and our DAO
used a JPA query to delete the user. The fix is shown in listing 18.21.
Regardless of this delete issue, the tests presented so far cover only the easy scenar-
ios: saving, loading, and deleting a simple user, with or without a telephone. It's a
good start but not enough; we need to test negative cases as well.
For the addUser() method, the only negative case is receiving a null reference.
It's always a good practice to check for method arguments and throw an Illegal-
AccessArgumentExeption if they don't comply. The getUserById() method has at
least two negative cases: handling an ID that doesn't exist in the database and load-
ing from an empty database. In our sample application, a null reference should be
returned in these cases (but another valid option would be to throw an exception).
Negative cases for removeUser() would be the same as for getUserById() , and in
our example they don't need to be tested because nothing happens when the user
doesn't exist (if an exception should be thrown, we should exercise these scenarios).
Listing 18.20 adds these new tests.

Listing 18.20 New test cases for negative scenarios

[...]
public class UserDaoJpaImplTest extends AbstractJpaDbUnitELTemplateTestCase {
[...]
@Test(expected=IllegalArgumentException. class )
public void testAddNullUser() throws Exception {
dao.addUser( null );
}

@Test
public void testGetUserByIdOnNullDatabase() throws Exception {
getUserReturnsNullTest(0);
}

@Test
@DataSets(setUpDataSet="/user.xml")
public void testGetUserByIdUnknownId() throws Exception {
getUserReturnsNullTest(666);
}

private void getUserReturnsNullTest( int deltaId) {
beginTransaction();
long id = ELFunctionMapperImpl.getId(User. class )+deltaId;