Not able to execute DataJpaTest

I have a spring-data-jpa repository called TagRepository. My spring-boot version is 2.1.2. I want to write a DataJpaTest for it. I have written the following code:

@RunWith(SpringRunner.class)
@DataJpaTest
@ContextConfiguration(classes={TagRepository.class})
public class TagRepositoryTest {

    @Autowired
    private TestEntityManager testEntityManager;

    @Autowired
    private TagRepository tagRepository;

    @Test
    public void findByTagTest() {
        Tag tag = new Tag("java");
        testEntityManager.persistAndFlush(tag);

        Optional<Tag> optionalTag = tagRepository.findByTag(tag.getTag());
        if(!optionalTag.isPresent()) {
            fail("Tag not found hence test failed");
        }

        assertThat(optionalTag.get()).isEqualTo(tag);
    }
}

However, when I execute the test it says Application failed to start and I get following error:

The bean 'tagRepository', defined in null, could not be registered. A bean with that name has already been defined in null and overriding is disabled.

Action:

Consider renaming one of the beans or enabling overriding by setting spring.main.allow-bean-definition-overriding=true