Testing with TypeScript Quiz

This quiz explores Testing with TypeScript, covering topics such as writing unit tests, using testing frameworks, and creating type-safe mocks. It emphasizes leveraging TypeScript’s type system for robust and maintainable tests while introducing popular testing tools and techniques.

Last Updated :
Discuss
Comments

Question 1

Why is TypeScript beneficial for writing unit tests?

  • It improves runtime performance of tests.

  • It ensures type safety and catches errors during compilation.

  • It eliminates the need for assertions in test cases.

  • It allows tests to run without a testing framework.

Discuss it

Question 2

Which of the following is a correct TypeScript test case?

TypeScript 
import { add } from "./math";

test("should add two numbers", () => {
    const result: number = add(2, 3);
    expect(result).toBe(5);
});


  • TypeScript does not support the test function.

  • The type of result must not be explicitly declared.

  • This is a correct TypeScript test case using a testing framework.

  • TypeScript tests must use the assert method instead of expect.

Discuss it

Question 3

Which testing framework is commonly used with TypeScript?

  • Mocha

  • Jest

  • Jasmine

  • All of the above

Discuss it

Question 4

How do you configure Jest to work with TypeScript?

  • Use the ts-jest package and update the Jest configuration file

  • Install typescript-jest and run jest --ts command.

  • Replace all .ts files with .js for testing.

  • Jest does not support TypeScript.

Discuss it

Question 5

What is type-safe mocking?

  • A process to mock runtime behaviors without using type definitions.

  • Creating mock implementations that adhere to the original type or interface.

  • Using only default exports for mock functions.

  • Replacing the actual implementation with an empty function.

Discuss it

Question 6

Which library helps create type-safe mocks in TypeScript?

  • jest-mock-typed

  • ts-mockito

  • sinon

  • All of the above

Discuss it

Question 7

How would you create a type-safe mock using Jest?

TypeScript 
interface UserService {
    getUser: (id: number) => string;
}

const mockUserService: jest.Mocked<UserService> = {
    getUser: jest.fn().mockReturnValue("Pranjal"),
};


  • Jest does not support type-safe mocking.

  • Use the jest.Mocked<T> utility for type-safe mocks.

  • Create mocks by directly implementing the interface.

  • Mocks do not require adherence to type definitions.

Discuss it

Question 8

Why is mocking important in unit tests?

  • To avoid testing external dependencies and isolate the system under test.

  • To replace all type checks with assertions.

  • To test multiple systems simultaneously.

  • To reduce the need for test cases.

Discuss it

Question 9

Which of the following is a valid use case for a test double?

  • To represent a function or object being replaced in a test.

  • To replace TypeScript’s type system with mocks.

  • To execute real implementations during testing.

  • To write tests without a testing framework.

Discuss it

Question 10

What does the following mock do?

TypeScript 
jest.spyOn(console, "log").mockImplementation(() => {});


  • Logs all console messages to the test output.

  • Replaces the console.log function with a mocked implementation.

  • Prevents console messages from being logged.

  • Deletes the console.log method entirely.

Discuss it

There are 10 questions to complete.

Take a part in the ongoing discussion