Spring Data: Service layer unit testing

Question

In my project I'm having trouble doing unit testing. One issue is that just doing an integration test is much faster to write and also tests that the components actually work together. Unit testing novel "algorithms" or so seems much easier. Unit Testing service classes it just feels wrong and useless.

I'm using mockito to mock spring data repository (and hence DB access). The thing is if i tell the mocked repository to return entity A on method call getById it will obviously return that and the service will return it too. Yes, the service does some extra stuff, but very minor things, like load lazy collections (from hibernate). Obviously I don't have any lazy collections (proxies) in a unit test.

Example:

@Test
public void testGetById() {
    System.out.println("getById");
    TestCompound expResult = new TestCompound(id, "Test Compound", "9999-99-9", null, null, null);

    TestCompoundRepository mockedRepository = mock(TestCompoundRepository.class);
    when(mockedRepository.findOne(id)).thenReturn(expResult);

    ReflectionTestUtils.setField(testCompoundService, "testCompoundRepository",
            mockedRepository, TestCompoundRepository.class);

    TestCompound result = testCompoundService.getById(id);
    assertEquals(expResult, result);
}

hooray, the rest succeeds. What a surprise! Not really no.

Can some one explain to me what I'm doing wrong? Or else what the point of such a test is? I mean I tell to return expResult and then it is returned. Wow. What a surprise! Feels like I'm testing if mockito works and not my Service.

EDIT:

The only benefit I see if some were stupid error happens like leaving an unwanted line there that sets return value to null or something similar stupid. Such cases would be caught by the unit test. Still the "reward-effort" ratio seems bad?

Answer 1

Question might be a bit old but I will put an answer in case someone stumbles across.

• I'm using Mockito and JUnit.
• AccountRepository is a plain spring data repository extending JPARepository.
• Account is a plain JPA entity.

To test your services and mock Spring Data repositories, you need something like below.

package foo.bar.service.impl;

import foo.bar.data.entity.Account;
import foo.bar.data.repository.AccountRepository;
import foo.bar.service.AccountService;

import org.junit.Assert;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.Mockito;
import org.mockito.runners.MockitoJUnitRunner;

@RunWith(MockitoJUnitRunner.class)
public class AccountServiceImplTest {

    @Mock
    private static AccountRepository accountRepository;

    @InjectMocks
    private static AccountService accountService = new AccountServiceImpl();

    private Account account;

    @Test
    public void testFindAccount() {

        Integer accountId = new Integer(1);

        account = new Account();
        account.setId(accountId);
        account.setName("Account name");
        account.setCode("Accont code");
        account.setDescription("Account description");

        Mockito.when(accountRepository.findOne(accountId)).thenReturn(account);

        Account retrivedAccount = accountService.findAccount(accountId);

        Assert.assertEquals(account, retrivedAccount);

    }

}

Answer 2

One of the reasons I like testing my Spring Data repositories is to test that I have defined my JPA mappings correctly. I do not use a mocking framework for these tests, I use the Spring Test framework which actually bootstraps the container allowing me to autowire the actual repository into the Junit test so that I may execute tests against it.

I agree with your thoughts that mocking the repository is pretty useless. Since your using Spring I would suggest leveraging the Spring Test framework to perform real tests against your repositories, which can be executed against an embedded database such as H2 in a more unit test based fashion or your actual database implementation such as Oracle or MySql, to conduct more of an integration test. (Execute these against a copy of a development database) These tests will reveal fallacies in your JPA mappings and other items such as improper cascades setup in the database.

Here is an example of one of my tests on GitHub. Notice how the framework actually autowires the repository into the test. The repository also contains an example of how to configure the Spring Test framework, which I have also demonstrated in this blog post.

In conclusion, I do not believe you will receive any of the benefits of testing a repository that I have discussed from using a mock of the repository.

One additional note I wanted to add, is that mocks are not really intended for use in the actual class under test. Their use is for providing required dependencies to a class under test.