Challenge - 5 Problems

🎖️

NestJS Testing Mastery

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Test your skills under time pressure!

🧠 Conceptual

intermediate

2:00remaining

Why is automated testing important in NestJS applications?

Which of the following best explains why automated testing improves reliability in NestJS apps?

AIt makes the app run faster by optimizing code during tests.

BIt catches bugs early by running tests automatically, preventing errors in production.

CIt replaces the need for developers to review code manually.

DIt automatically fixes bugs without developer input.

Attempts:

2 left

❓ component_behavior

intermediate

2:00remaining

What happens when a NestJS service test fails?

Given a NestJS service with a failing unit test, what is the immediate effect on application reliability?

NestJS

describe('CatsService', () => {
  let service: CatsService;

  beforeEach(() => {
    service = new CatsService();
  });

  it('should return all cats', () => {
    expect(service.findAll()).toEqual(['cat1', 'cat2']);
  });

  it('should add a cat', () => {
    service.addCat('cat3');
    expect(service.findAll()).toContain('cat3');
  });

  it('should fail this test', () => {
    expect(service.findAll().length).toBe(0);
  });
});

AThe app will crash immediately in production.

BThe service automatically fixes the bug causing the failure.

CThe failing test signals a bug, prompting fixes before deployment, improving reliability.

DThe test failure is ignored and does not affect reliability.

Attempts:

2 left

❓ state_output

advanced

2:00remaining

What is the output of this NestJS controller test?

Consider this test for a NestJS controller method. What will the test output be?

NestJS

import { Test, TestingModule } from '@nestjs/testing';
import { AppController } from './app.controller';

describe('AppController', () => {
  let appController: AppController;

  beforeEach(async () => {
    const app: TestingModule = await Test.createTestingModule({
      controllers: [AppController],
    }).compile();

    appController = app.get<AppController>(AppController);
  });

  it('should return Hello World', () => {
    expect(appController.getHello()).toBe('Hello World!');
  });

  it('should fail this test', () => {
    expect(appController.getHello()).toBe('Hello');
  });
});

AOne test passes, one test fails with an error.

BBoth tests pass successfully.

CBoth tests fail with errors.

DThe test suite does not run due to syntax errors.

Attempts:

2 left

📝 Syntax

advanced

2:00remaining

Which option causes a syntax error in a NestJS test file?

Identify the option that will cause a syntax error when running a NestJS test.

NestJS

describe('Sample Test', () => {
  it('should pass', () => {
    expect(true).toBe(true);
  });
});

Adescribe('Test', () => { it('runs', () => { expect(true).toBe(true) }) });

Bdescribe('Test', () => { it('runs', () => { expect(true).toBe(true); }); });

Cdescribe('Test', () => { it('runs', () => { expect(true).toBe(true); } ); });

Ddescribe('Test', () => { it('runs', () => { expect(true).toBe(true); ); });

Attempts:

2 left

🔧 Debug

expert

2:00remaining

Why does this NestJS test fail with a timeout error?

Examine the following test code. Why does it fail with a timeout?

NestJS

describe('Async Test', () => {
  it('should complete async operation', () => {
    setTimeout(() => {
      expect(true).toBe(true);
    }, 1000);
  });
});

AThe test does not return a Promise or use done callback, so Jest times out waiting.

BThe setTimeout duration is too short to complete the test.

CThe expect statement is incorrect and causes an error.

DThe test passes immediately without waiting for setTimeout.

Attempts:

2 left