Injecting automapper in unit tests?

[bfahm]

I'm trying to inject automapper when creating a testing module, but i'm getting an error because Mapper is an interface not a class.

const module = await Test.createTestingModule({
      providers: [
        AddressService,
        { provide: AddressesRepository, useFactory: mockAddressesRepository },
        { provide: Mapper, useFactory: mockMapper },
      ],
    }).compile();

I'm using the library with NestJS
How could I use the library alongside my unit tests?

[nartc]

@bfahm You should use getMapperToken() utility for the provide there.

If you use InjectMapper('name_goes_here') then use { provide: getMapperToken('name_goes_here'), .. }.
If you use InjectMapper() then use { provide: getMapperToken(), ... }

I can update docs ASAP to mention this. Thank you for asking!

[micalevisk]

I guess the only way is by using the createMapper from @automapper/core

I've been using it to check if all props are being mapped properly.

[nartc]

I think that's where the Profile comes in. I can probably expose a static function from AutomapperProfile so you can get the returned value of mapProfile() to use in the test

{
   provide: getMapperToken(),
   useValue: createMapper({...}) // this can be a utility
}

// get the provided mapper
const testMapper = Something.get(getMapperToken());
testMapper.addProfile(SomeProfile.getProfile()); // should be the profile you want to test against

[micalevisk]

or even

[nartc]

Yeah absolutely

[bfahm]

I really appreciate the support! It worked.

[BeyondBelief96]

Hey, I've run into this issue as well and the above answer by @nartc worked for me in terms of getting the dependency resolving, but how do we go about mocking the actual map() function? I have a profile with 2 different mappings like so

`@Injectable()
export class LoanDtoMapper extends AutomapperProfile {
constructor(@InjectMapper('loan-mapper') loanMapper: Mapper) {
super(loanMapper);
}

mapProfile(): MappingProfile {
return (mapper) => {
mapper.createMap(LoanRequestDto, Loan);
mapper.createMap(Loan, LoanResponseDto);
};
}`

and my mockLoanMapper:

export const mockLoanMapper = {
map: jest.fn()
}

but how do I mock the map function to return the correct object given that the mapping function depends on the types specified. Like if the map function is called with the mockLoan object of type Loan, i want the mockLoanResponseDto to be returned. But if the map() function is called with the mockLoanInputDto, I want the map function to return the mockLoan object.

[nartc]

You could probably use something like jest-when https://www.npmjs.com/package/jest-when

[micalevisk]

another (unrelated) tip for tests in nestjs: @golevelup/ts-jest

[BeyondBelief96]

Thanks! I'll look into those.