NestJS Quiz ( Intermediate ) - All Questions

This intermediate NestJS quiz is designed for developers who know the basics and want to test real-world usage of NestJS. It covers dependency injection scopes, modules communication, guards, interceptors, pipes, middleware flow, validation, authentication basics, and common interview scenarios.

Question 1: What is the main responsibility of AppModule in NestJS?

Handle routing
Bootstrap the application
Group feature modules
Configure middleware

Explanation: AppModule groups and imports all feature modules.

Question 2: How does NestJS resolve dependencies by default?

Factory pattern
Singleton instances
Prototype instances
Manual injection

Explanation: NestJS providers are singleton by default.

Question 3: Which provider scope creates a new instance per request?

DEFAULT
STATIC
REQUEST
TRANSIENT

Explanation: REQUEST scope creates a provider per request.

Question 4: Which provider scope creates a new instance every injection?

DEFAULT
REQUEST
GLOBAL
TRANSIENT

Explanation: TRANSIENT creates a new instance on every injection.

Question 5: How can a provider be shared across modules?

Declare it again
Export it from a module
Use global variables
Import main.ts

Explanation: Exporting a provider allows reuse across modules.

Question 6: What is the purpose of @Global() decorator?

Create global routes
Make a module globally available
Enable middleware globally
Register controllers

Explanation: @Global makes providers available across the app.

Question 7: Which NestJS feature is executed before route handlers?

Interceptors
Guards
Pipes
Exception filters

Explanation: Guards run before route handlers for authorization.

Question 8: What is the primary role of Guards?

Data validation
Authorization logic
Response mapping
Error handling

Explanation: Guards determine whether a request is allowed.

Question 9: Which interface must a Guard implement?

CanActivate
NestGuard
AuthGuard
Activate

Explanation: Guards implement the CanActivate interface.

Question 10: Which NestJS feature transforms incoming request data?

Interceptors
Guards
Pipes
Middleware

Explanation: Pipes transform and validate input data.

Question 11: Which pipe converts a string parameter to number?

ValidationPipe
ParseIntPipe
DefaultValuePipe
TransformPipe

Explanation: ParseIntPipe converts strings to numbers.

Question 12: What does ValidationPipe rely on?

Joi
class-validator
Zod
AJV

Explanation: ValidationPipe uses class-validator.

Question 13: Which decorator enables global pipes?

app.usePipe()
app.useGlobalPipes()
@UsePipes()
@GlobalPipe()

Explanation: useGlobalPipes applies pipes globally.

Question 14: Which feature wraps method execution for extra logic?

Middleware
Guards
Interceptors
Filters

Explanation: Interceptors wrap method execution.

Question 15: Which common use case fits Interceptors?

Authentication
Authorization
Logging and response mapping
Input validation

Explanation: Interceptors are used for logging and transformation.

Question 16: What is the execution order in NestJS request lifecycle?

Middleware → Guards → Pipes → Interceptors → Controller
Guards → Middleware → Pipes → Controller
Pipes → Guards → Interceptors → Middleware
Interceptors → Guards → Pipes → Controller

Explanation: This is the correct execution sequence.

Question 17: Which feature catches and formats thrown errors?

Guards
Interceptors
Exception filters
Middleware

Explanation: Exception filters handle errors.

Question 18: Which base class handles HTTP exceptions?

BaseException
HttpError
HttpException
NestException

Explanation: HttpException is used for HTTP errors.

Question 19: Which decorator applies exception filters?

@UseFilters()
@Catch()
@Filter()
@HandleError()

Explanation: @UseFilters applies exception filters.

Question 20: What is middleware mainly used for?

Authorization
Request preprocessing
Response mapping
Error handling

Explanation: Middleware runs before route handling.

Question 21: Which middleware type is NOT supported by NestJS?

Class-based
Function-based
Third-party
Decorator-based

Explanation: NestJS does not support decorator-based middleware.

Question 22: Which decorator injects the request object?

@Req()
@Request()
@Body()
@Ctx()

Explanation: @Req accesses the request object.

Question 23: Which decorator injects response object?

@Res()
@Response()
@Reply()
@Out()

Explanation: @Res injects the response object.

Question 24: What happens when using @Res() without passthrough?

NestJS auto-handles response
You must manually send response
Interceptor still works
Pipe validation fails

Explanation: Manual response handling is required.

Question 25: Which feature supports authentication strategies?

Passport
JWT
OAuth
Guards

Explanation: NestJS integrates with Passport.

Question 26: Which Passport strategy is commonly used for JWT?

LocalStrategy
JwtStrategy
OAuthStrategy
SessionStrategy

Explanation: JwtStrategy handles JWT authentication.

Question 27: Which decorator extracts authenticated user?

@Req()
@User()
@Auth()
Custom decorator

Explanation: Custom decorators extract user data.

Question 28: Which module registers environment variables?

ConfigModule
EnvModule
DotenvModule
SystemModule

Explanation: ConfigModule manages environment variables.

Question 29: Which method enables global configuration?

ConfigModule.setup()
ConfigModule.forRoot()
ConfigModule.init()
ConfigModule.load()

Explanation: forRoot loads config globally.

Question 30: Which decorator marks a route as public using custom guards?

@Open()
@Public()
@Allow()
Custom decorator

Explanation: Public routes require a custom decorator.

Question 31: Which NestJS feature enables modular scalability?

Providers
Modules
Controllers
Pipes

Explanation: Modules enable scalable architecture.

Question 32: What does forwardRef() solve?

Lazy loading
Circular dependency issues
Async imports
Route conflicts

Explanation: forwardRef resolves circular dependencies.

Question 33: Which scenario requires forwardRef?

Module-to-module reference
Circular module dependency
Service injection
Middleware injection

Explanation: Used when modules depend on each other.

Question 34: Which lifecycle hook runs on module initialization?

onInit()
beforeInit()
onModuleInit()
afterInit()

Explanation: onModuleInit runs after module creation.

Question 35: Which lifecycle hook runs before app shutdown?

beforeExit()
onDestroy()
beforeShutdown()
enableShutdownHooks

Explanation: beforeShutdown runs during shutdown.

Question 36: Which feature supports GraphQL in NestJS?

@nestjs/graphql
apollo-server
graphql-js
TypeGraphQL

Explanation: @nestjs/graphql integrates GraphQL.

Question 37: Which transport layer supports microservices?

HTTP only
TCP, Redis, NATS
WebSocket only
gRPC only

Explanation: NestJS supports multiple transports.

Question 38: Which decorator defines message patterns?

@Event()
@MessagePattern()
@Subscribe()
@Handle()

Explanation: @MessagePattern handles microservice messages.

Question 39: Which feature improves testability in NestJS?

Decorators
Dependency Injection
Controllers
Modules

Explanation: DI enables easy mocking in tests.

Question 40: Which testing utility creates a testing module?

NestFactory
Test.createTestingModule()
TestingModule
NestTest

Explanation: createTestingModule is used in tests.

Question 41: Which file configures build options?

package.json
nest-cli.json
tsconfig.json
main.ts

Explanation: nest-cli.json controls build config.

Question 42: Which command builds NestJS for production?

nest serve
npm run build
nest start --prod
npm start

Explanation: npm run build creates production build.

Question 43: Which feature supports REST and GraphQL together?

Controllers
Resolvers
Hybrid application
Middleware

Explanation: NestJS supports hybrid apps.

Question 44: Which practice improves NestJS performance?

Heavy middleware usage
Stateless services
Request-scoped providers everywhere
Manual DI

Explanation: Stateless services scale better.

Question 45: What is the main architectural advantage of NestJS?

Minimal setup
Opinionated and scalable structure
Frontend rendering
Database abstraction

Explanation: NestJS enforces scalable architecture.

Question 46: What is the ultimate goal of NestJS?

Static APIs
Scalable server-side applications
CLI tooling
Microservices only

Explanation: NestJS is built for scalable backend systems.

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NestJS Quiz ( Intermediate )

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NestJS Quiz ( Intermediate )