Unit testing controllers in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the testing module for a NestJS controller test.

NestJS

import { Test, TestingModule } from '@nestjs/[1]';

Drag options to blanks, or click blank then click option'

Acore

Bcommon

Ctesting

Dplatform-express

Attempts:

3 left

💡 Hint

Common Mistakes

Importing from '@nestjs/common' instead of '@nestjs/testing'.

Using '@nestjs/core' which is for core framework features.

In NestJS, the testing utilities are imported from '@nestjs/testing'. This module helps create a testing environment for controllers and services.

2fill in blank

medium

Complete the code to create a testing module for the controller named 'CatsController'.

NestJS

const moduleRef: TestingModule = await Test.createTestingModule({ controllers: [[1]] }).compile();

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ACatsController

BDogsController

CBirdsController

DFishController

Attempts:

3 left

💡 Hint

Common Mistakes

Using a different controller name than the one being tested.

Forgetting to include the controller in the testing module.

When testing a controller, you include it in the 'controllers' array of the testing module. Here, we want to test 'CatsController'.

3fill in blank

hard

Fix the error in retrieving the controller instance from the testing module.

NestJS

const controller = moduleRef.[1](CatsController);

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Aget

BgetController

Cretrieve

Dfetch

Attempts:

3 left

💡 Hint

Common Mistakes

Using non-existent methods like 'getController' or 'fetch'.

Trying to access the controller directly without using 'get'.

To get an instance of a provider or controller from the testing module, use the 'get' method.

4fill in blank

hard

Fill both blanks to mock a service method and test the controller's response.

NestJS

jest.spyOn(service, '[1]').mockImplementation(() => [2]);

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AfindAll

B[{ id: 1, name: 'Fluffy' }]

Creturn 'Hello'

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Mocking the wrong method name.

Returning a wrong type like a string instead of an array.

We spy on the 'findAll' method of the service and mock it to return a list of cats. This helps test the controller without calling the real service.

5fill in blank

hard

Fill all three blanks to write a test that checks if the controller's getAll method returns the mocked data.

NestJS

it('should return an array of cats', async () => {
  const result = await controller.[1]();
  expect(result).toEqual([2]);
  expect(service.[3]).toHaveBeenCalled();
});

Drag options to blanks, or click blank then click option'

AgetAll

B[{ id: 1, name: 'Fluffy' }]

CfindAll

Dcreate

Attempts:

3 left

💡 Hint

Common Mistakes

Using wrong method names in controller or service.

Not matching the expected data with the mocked return.

The test calls the controller's 'getAll' method, expects the mocked array, and checks that the service's 'findAll' method was called.