1. First, we will create a new MockPublisherRepositoryTests test class in the src/test/java/com/example/bookpub directory at the root of our project with the following content:

import static org.assertj.core.api.Assertions.assertThat;
import static org.mockito.BDDMockito.given;
import static org.mockito.BDDMockito.reset; 
 
@RunWith(SpringRunner.class) 
@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.NONE) 
public class MockPublisherRepositoryTests { 
    @MockBean 
    private PublisherRepository repository; 
 
    @Before 
    public void setupPublisherRepositoryMock() { 
        given(repository.count()).willReturn(5L); 
    } 
 
    @Test 
    public void publishersExist() { 
        assertThat(repository.count()).isEqualTo(5L); 
    } 
 
    @After 
    public void resetPublisherRepositoryMock() { 
        reset(repository); 
    } 
} 

2. Execute the tests by running ./gradlew clean test and the tests should get passed