In the following `DonorRepository` methods:
`findDonorCodeGroupsByDonor(Donor donor)`
`findDonorDonorCodesOfDonor(Donor donor)`
it would be preferable to pass in `String donorId`, rather than the Donor object. You can then use:
`Donor donor = findDonorById(donorId);` within the repository method to get the Donor.
Please refactor these methods, and usage of the methods, to make use of this.
The test cases can then be updated to not make use of the `donorRepository.findDonorById()` method, and you can use `donorRepository.findDonorCodeGroupsByDonor(1l)` and `donorRepository.findDonorDonorCodesOfDonor(1l)` rather.