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/ 2 Years ago, sun, january 30, 2022, 12:00:00
I'm trying to write a unit test for my NestJS API, but I'm getting this TypeError: Cannot read property 'then' of undefined error when I try to simulate a method in my service class. Could you please explain what is wrong with my code ?
sercice:
async userExist(data: User): Promise<boolean> {
return new Promise((resolve, reject) => {
this.usereRepository
.findOne({
where: {
name: data.name,
},
})
.then((res) => {
if (!res) {
resolve(false);
}
resolve(true);
})
.catch((err) => {
reject(err);
});
});
}
async createUser(data: User): Promise<User> {
return new Promise((resolve, reject) => {
this.userExist(data).then((exist) => {
if (exist) {
return reject('User already exist');
}
this.userRepository
.save(data)
.then((res) => {
resolve(res);
})
.catch((err) => {
reject(err);
});
});
});
}
service.test:
it('should create a new user without error', async () => {
jest
.spyOn(service, 'userExist')
.mockImplementation(() => Promise.resolve(false));
await service.createUser(data);
expect(userRepository.save).toHaveBeenCalled();
});
I don't know if this is helpful, but I put the beforeEach where I mock my save and findOne database functions.
let service: UserService;
let userRepository: Repository<User>;
beforeEach(async () => {
const module: TestingModule = await Test.createTestingModule({
providers: [
UserService,
{
provide: getRepositoryToken(User),
useValue: {
save: jest.fn(),
findOne: jest.fn(),
},
},
],
}).compile();
service = module.get<UserService>(UserService);
userRepository = module.get<Repository<User>>(
getRepositoryToken(User)
);
});
error trace
TypeError: Cannot read property 'then' of undefined
64 | if (exist) {
65 | return reject('User already exist');
> 66 | }
| ^
67 | this.userRepository
68 | .save(data)
69 | .then((res) => {
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