Testing with TypeScript Quiz (original) (raw)

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.

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.

Which testing framework is commonly used with TypeScript?

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.

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.

Which library helps create type-safe mocks in TypeScript?

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

TypeScript `

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

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

`

• Jest does not support type-safe mocking.
• Use the jest.Mocked utility for type-safe mocks.
• Create mocks by directly implementing the interface.
• Mocks do not require adherence to type definitions.

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.

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.

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.

There are 10 questions to complete.

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