@RunWith(SpringRunner.class)
@SpringBootTest(classes = App.class) 

org.springframework.beans.factory.UnsatisfiedDependencyException:
 Error creating bean with name 'com.springboot.LibrarySystem.mapper.UserMapperTest':
 Unsatisfied dependency expressed through field 'userMapper'; 
 nested exception is org.springframework.beans.factory.NoSuchBeanDefinitionException:
 No qualifying bean of type 'com.sb.LibrarySystem.mapper.UserMapper' 
 available: expected at least 1 bean which qualifies as autowire candidate. 
 Dependency annotations: {@org.springframework.beans.factory.annotation.Autowired(required=true)}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = Application.class)
public class UserMapperTest {

}

@RunWith(SpringRunner.class)
@SpringBootTest(classes = App.class)
public class UserMapperTest {