Assuming we are doing TDD, let's build up the TestCase first.
We are going to build up a typical API to create Person with bunch of addresses.
To understand how this works, we will create a buggy Service and include background Audit mechanism, to simulate abstraction to developer.
@RunWith(SpringJUnit4ClassRunner.class)
public class PersonServiceTest {
@Autowired
private PersonService personService;
@Before
public void insertData() {
TestUtil.createTestData(personService);
}
@Before
public void cleanup() {
QueryCountHolder.clear();
}
@Test(timeout = 500)
public void testAddressCount() {
assertThat(QueryCountHolder.getGrandTotal().getTotalNumOfQuery(), is(0));
assertThat(personService.getAddressCount("John"), is(2));
assertThat(QueryCountHolder.getGrandTotal().getTotalNumOfQuery(), is(1));
}
@Test(timeout = 500)
public void testUpdatePerson() throws Exception {
assertThat(QueryCountHolder.getGrandTotal().getTotalNumOfQuery(), is(0));
Person person = personService.getCustomerByName("John");
assertThat(person.getGender(), CoreMatchers.nullValue());
person.setGender("Male");
QueryCountHolder.clear();
personService.save(person);
assertThat(QueryCountHolder.getGrandTotal().getTotalNumOfQuery(), is(3));
person = personService.getCustomerByName("John");
assertThat(person.getGender(), CoreMatchers.is("Male"));
}
}
testAddressCount - Based on the service interface, this test case assume 1 sql is executed to get the count of addresses give a first name
testUpdatePerson - We update the person gender, and assume 3 sqls are executed.
- To read the person
- Update gender
- Audit event to record gender change
testAddressCount java.lang.AssertionError: Expected: is <1> got: <2>
testUpdatePerson java.lang.AssertionError: Expected: is <3> got: <4>
Let's dive deep into the service and see what is wrong.
@Service
public class PersonServiceImpl implements PersonService {
@Autowired
private PersonRepository repository;
@Transactional(readOnly = true, propagation = Propagation.SUPPORTS)
public int getAddressCount(String firstName) {
List<Person> list = repository.findByFirstNameLike(firstName);
if (list == null) {
return 0;
}
Person byFirstNameLike = list.get(0);
return byFirstNameLike == null ? 0 : byFirstNameLike.getAddresses().size();
}
@Transactional(readOnly = false, propagation = Propagation.SUPPORTS)
public Person save(Person person) {
// un intended operation
person.setLastName(person.getLastName() + " 1");
return repository.save(person);
}
}
As you can see in getAddressCount, instead of writing a custom hql, the developer did an mistake of reading object and doing a size on the list. The correct way of writing this method is to make use of custom query which does a count(*) on address table.
Similarly with Save, the test expected to update Gender, but the service was doing something more than expected, triggering a unexpected audit record on last name.
To demonstrate this article I have made use of datasource-proxy which is very good API to capture sqls that hibernate or any other ORM frameworks execute under the hood.
Also, I feel like it is very good practice to use @Test(timeout) so we know if some one changes a method later on, and hinder the SLA.
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