Exploring the world of mocking tests using Jest and inputs

Question

Exploring the world of mocking tests using Jest and inputs

Is there a way to create a jest test specifically for this function?

const input = require('prompt-sync')();

export function choices(): void {
    const choice = input("Choose a letter");
    if (choice === "a") {
        console.log("Airplane");
    } if (choice === "b") {
        console.log("Balloon");
    } else {
        console.log("Neither");
    }

}

I am aware that mocking is necessary in this scenario. However, I am uncertain about how to implement it when the input is stored within the function itself rather than being passed as a parameter. I would prefer not to alter this setup.

typescript input jestjs

Answer 1

Answer №1

To mock the prompt-sync module in your tests, you can utilize the jest.mock function. This module returns a function that provides your input, so your Jest.mock setup would look something like this:

const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);

Make sure to include this setup before importing the module in your test file.

Here is a complete example:

const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);

import { choices } from "../path/to/file";

describe("test", () => {
  let consoleSpy: jest.SpyInstance;

  beforeEach(() => {
    consoleSpy = jest.spyOn(console, "log");
  });

  afterEach(() => {
    jest.resetAllMocks();
  });

  it("should call the input", () => {
    choices();

    expect(mockInput).toHaveBeenCalledWith("Choose a letter");
  });

  it("should call 'A'", () => {
    mockInput.mockReturnValue("a");

    choices();

    expect(consoleSpy).toHaveBeenCalledWith("Airplane");
  });
});

I recommend refactoring your code to improve its testability.

Answer 2

To mock the prompt-sync module in your tests, you can utilize the jest.mock function. This module returns a function that provides your input, so your Jest.mock setup would look something like this:

const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);

Make sure to include this setup before importing the module in your test file.

Here is a complete example:

const mockInput = jest.fn();
jest.mock("prompt-sync", () => () => mockInput);

import { choices } from "../path/to/file";

describe("test", () => {
  let consoleSpy: jest.SpyInstance;

  beforeEach(() => {
    consoleSpy = jest.spyOn(console, "log");
  });

  afterEach(() => {
    jest.resetAllMocks();
  });

  it("should call the input", () => {
    choices();

    expect(mockInput).toHaveBeenCalledWith("Choose a letter");
  });

  it("should call 'A'", () => {
    mockInput.mockReturnValue("a");

    choices();

    expect(consoleSpy).toHaveBeenCalledWith("Airplane");
  });
});

I recommend refactoring your code to improve its testability.

Exploring the world of mocking tests using Jest and inputs

Answer №1

Similar questions

Angular 6 provides a regular expression that specifically targets the removal of any characters that are not numbers and enforces the allowance of

transfer item between a mother and offspring

Creating an interface for writing types in Firebase functions/storage/database

Updating a null value within the database was done successfully

Creating an Angular table using reactive forms: a step-by-step guide

How can models be aggregated in SQL by connecting them through other models?

Remove the package from the @types folder within the node_modules directory

Building a Vuetify Form using a custom template design

Leverage the specific child's package modules during the execution of the bundle

When using React with TypeScript, there seems to be an issue where using history.push to change the URL results in rendering the 404 page instead

Tips for testing the 'error' color (red) in Material UI using Jest and React Testing Library

What is the best way to showcase a standalone JSON object within the template?

Arrange the array based on the order of the enumeration rather than its values

Obtaining undefined values for req and resolvedUrl in GetServerSideProps function

What are the steps for creating a standalone build in nextJS?

Is there a different approach available since the array function "some" does not restrict type even when a type predicate is implemented?

Retrieve TypeScript object after successful login with Firebase

Basic exam but located in a place that is not valid

The presence of a method is triggering an Error TS2741 message stating that the property is missing in type

Angular is reporting that the check-in component is nonexistent