Can not implement my test class - Null Pointer Exception

I have a method in my service implementation class and i can not add correctly it's testing method. It gives me Null pointer exception. Spring Boot project - JUnit 5.

Method
public Page<CompanyGroup> findByNameContainingIgnoreCase(String name, Pageable pageable) {
        log.debug("Request to query all CompanyGroups");
        Page<CompanyGroup> result = companyGroupRepository.findByNameContainingIgnoreCase(name, pageable);
        return result;
    }

Test Method

 void findByNameContainingIgnoreCase() {

        Pageable pageable = PageRequest.of(0, 5, Sort.by(
                Sort.Order.asc("name"),
                Sort.Order.desc("id")));
        Page<CompanyGroup> result;

        result = companyGroupRepository.findByNameContainingIgnoreCase("thrylos", pageable);
        assertEquals(0, result.getTotalElements());
        result = companyGroupService.findByNameContainingIgnoreCase("Olympiakos", pageable);
        assertEquals(1, result.getTotalElements());
        result = companyGroupService.findByNameContainingIgnoreCase("olympiakos", pageable);
        assertEquals(1, result.getTotalElements());
    }