NestJs - Jest - Testing: ConnectionNotFoundError: Connection "default" was not found - testing

Question

I am trying to write a test of a simple TODO App.
This is my service test class:
const mockTaskRepository = () => ({
createTask: jest.fn(),
});
describe('TasksService', () => {
let tasksService;
let taskRepository;
beforeEach(async () => {
const module = await Test.createTestingModule({
providers: [TasksService, { provide: TaskRepository, useFactory: mockTaskRepository }],
}).compile();
tasksService = await module.get<TasksService>(TasksService);
taskRepository = await module.get<TaskRepository>(TaskRepository);
});
describe('create task', () => {
it('calls taskRepository.create() and returns the result', async () => {
const createTaskDto = {
title: 'Test task',
description: 'Test desc',
};
taskRepository.createTask.mockResolvedValue('someTask');
expect(taskRepository.createTask).not.toHaveBeenCalled();
const result = await tasksService.createTask(createTaskDto);
expect(taskRepository.createTask).toHaveBeenCalledWith(createTaskDto);
expect(result).toEqual('someValue');
});
});
});
And this is my task service:
#Injectable()
export class TasksService {
constructor(
#InjectRepository(TaskRepository)
private taskRepository: TaskRepository,
) {}
async createTask(createTaskDto: CreateTaskDto): Promise<Task> {
const { title, description } = createTaskDto;
const task = new Task();
task.title = title;
task.description = description;
task.status = TaskStatus.IN_PROGRESS;
await task.save();
return task;
}
}
When I try to run the Create a Task test, the error below occurs.
FAIL src/tasks/tasks.service.spec.ts
● TasksService › create task › calls taskRepository.create() and returns the result
ConnectionNotFoundError: Connection "default" was not found.
at new ConnectionNotFoundError (error/ConnectionNotFoundError.ts:8:9)
at ConnectionManager.Object.<anonymous>.ConnectionManager.get (connection/ConnectionManager.ts:40:19)
at Object.getConnection (index.ts:247:35)
at Function.Object.<anonymous>.BaseEntity.getRepository (repository/BaseEntity.ts:85:72)
at Task.Object.<anonymous>.BaseEntity.save (repository/BaseEntity.ts:50:42)
at TasksService.createTask (tasks/tasks.service.ts:35:14)
at Object.<anonymous> (tasks/tasks.service.spec.ts:69:38)
Test Suites: 1 failed, 1 passed, 2 total
Tests: 1 failed, 8 passed, 9 total
Anyone know what's the mistake in the code?
..........................................
Thanks in advance!

Answer 1

If it is looking for connection default then I assume that the TypeOrmModule configs are still being taken into account. Instead of provide: TaskRepository try changing it to provide: getRepositoryToken(TaskEntity) if you have a TaskEntity. This will tell Nest to override the default repo that the #InjectRepository() decorator tries to provide.
If that isn't the case, do you think you could add your TaskService and TaskModule classes as well?

Answer 2

You should mock the repository then bringing up the context of Test Module. Otherwise, the real Repository is being injected (via Nest's DI) into service.
const module = await Test.createTestingModule({
providers: [
{
provide: getRepositoryToken(YourEntityClass),
useValue: mockedRepo, // or use class
},
TasksService],
}).compile();
tasksService = await module.get<TasksService>(TasksService);
// taskRepository = await module.get<TaskRepository>(TaskRepository); don't have to do that if `useValue` was used instead of factory
So, TL;DR :
provide: TaskRepository should provide Token of given Injectable in this case: https://docs.nestjs.com/fundamentals/custom-providers#non-class-based-provider-tokens

Answer 3

The test expected method Repository.createTask to be called, but method Service.createTask didn't make that call.
The fix: Update the Service method to delegate to the Repository method the task creation.
// tasks.service.ts
async createTask(createTaskDto: CreateTaskDto, user: User): Promise<Task> {
return this.taskRepository.createTask(createTaskDto, user);
}
// tasks.repository.ts
async createTask(createTaskDto: CreateTaskDto, user: User): Promise<Task> {
const { title, description } = createTaskDto;
const task = new Task();
task.title = title;
task.user = user;
task.description = description;
task.status = TaskStatus.IN_PROGRESS;
await task.save();
delete task.user;
return task;
}
}