Unit testing services in NestJS - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to import the testing module for a NestJS service.

NestJS

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

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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.

The NestJS testing utilities are imported from '@nestjs/testing' to create a testing module.

2fill in blank

medium

Complete the code to create a testing module for the service.

NestJS

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

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AMyService

BAppController

CConfigService

DHttpModule

Attempts:

3 left

💡 Hint

Common Mistakes

Adding controllers or modules instead of the service in providers.

Forgetting to include the service in the testing module.

The service to be tested must be listed in the providers array to be instantiated in the testing module.

3fill in blank

hard

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

NestJS

const service = module.[1](MyService);

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AgetService

Bget

Cfetch

Dretrieve

Attempts:

3 left

💡 Hint

Common Mistakes

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

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

The correct method to get a provider instance from the testing module is 'get'.

4fill in blank

hard

Fill both blanks to mock a dependency service in the testing module.

NestJS

providers: [MyService, { provide: [1], useValue: [2] }]

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ADependencyService

BMockDependency

CMyService

DRealDependency

Attempts:

3 left

💡 Hint

Common Mistakes

Using the service under test as the dependency token.

Using the real dependency instead of a mock.

To mock a dependency, provide its token and a mock value in the providers array.

5fill in blank

hard

Fill all three blanks to write a test that checks if the service method returns expected data.

NestJS

expect(await service.[1]()).toEqual([2]); jest.spyOn(service, '[3]');

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AgetData

B{ id: 1, name: 'Test' }

DfetchData

Attempts:

3 left

💡 Hint

Common Mistakes

Using different method names in expect and spyOn.

Expecting wrong data structure or value.

The test calls 'getData' method, expects a specific object, and spies on 'getData' to check calls.