NestJS Technology & Digital Applications 3

Question 1

In NestJS, which decorator registers a class as a middleware?

Accepted Answer

@Injectable() combined with NestMiddleware interface

Answer

Middleware classes must be decorated with @Injectable() and implement the NestMiddleware interface which requires a use() method.

Question 2

What does the `forwardRef()` utility solve in NestJS?

Accepted Answer

Circular dependency issues between modules or providers

Answer

forwardRef() resolves circular dependencies where two classes depend on each other by deferring reference resolution.

Question 3

Which decorator in NestJS is used to extract a specific property from a request object?

Accepted Answer

@Body()

Answer

@Body() extracts the entire request body or a named property from it, while @Req() provides the full request object.

Question 4

In NestJS testing, what does `Test.createTestingModule()` return?

Accepted Answer

A TestingModuleBuilder used to compile and create a testing module

Answer

Test.createTestingModule() returns a TestingModuleBuilder, which you then call .compile() on to get the actual TestingModule.

Question 5

What is the function of `APP_GUARD` token in NestJS?

Accepted Answer

Registers a guard globally across all routes without @UseGuards() on every controller

Answer

Providing a guard with the APP_GUARD token in any module registers it as a global guard applied to every route in the application.

NestJS Practice Test