NestJS Research & Evidence-Based Practice 3

Question 1

Evidence-based NestJS testing practice recommends using which testing module to create an isolated module context for unit tests?

Accepted Answer

TestingModule from @nestjs/testing

Answer

Test.createTestingModule() from @nestjs/testing creates an isolated NestJS application context suitable for unit and integration testing.

Question 2

Based on NestJS e2e testing patterns, which HTTP testing library is most commonly used alongside supertest to make requests against the app?

Accepted Answer

supertest

Answer

Supertest is the standard library used in NestJS e2e tests to make HTTP requests against the running application instance.

Question 3

When researching best practices, which NestJS testing approach verifies that a service method calls a repository method with correct arguments without hitting the database?

Accepted Answer

Unit testing with mocked providers

Answer

Unit testing with mocked providers (using jest.fn() or createMock()) isolates the service under test from its real dependencies.

Question 4

Documentation research reveals that NestJS provides which decorator to override a provider with a mock value in a testing module?

Accepted Answer

Both A and C are correct

Answer

Both useValue and useFactory are valid override strategies in the testing module's providers array, serving different needs.

Question 5

Based on evidence from NestJS documentation, which Jest configuration option is set in jest.config.js to map TypeScript path aliases in test files?

Accepted Answer

moduleNameMapper

Answer

moduleNameMapper maps TypeScript path aliases (like @app/*) to their actual file paths so Jest can resolve them during tests.

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NestJS Research & Evidence-Based Practice 3