In this article i am gone to share Programming with JavaScript by meta Week 4 | Programming Assignment: Writing a Unit Test Solution with you..

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Lab Instructions: Unit Testing

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Task 1: Add Jest as a devDependency

Open terminal. Make sure that it’s pointing to jest-testing directory.
Install the jest npm package using the npm install command and the –save-dev flag.
Verify that the installation was completed successfully by opening the package.json file and confirming that the “devDependencies” entry lists jest similar to the following:

"devDependencies": {
    "jest": "^28.0.0"
}

Task 2: Update the test entry

In the package.json file, locate the “scripts” entry, and inside of it, update the test entry to jest.

Task 3: Code the timesTwo function

Open the timesTwo.js file and add a function named timesTwo. The function should take number as input and return the value 2 multiplied by the number. Export the timesTwo function as a module.

Task 4: Write the first test

Code a test call with the following arguments:

1. The description that reads: “returns the number times 2”.
2. The second argument should expect the call to the timesTwo function, when passed the number 10, to be 20.

Task 5: Run the first test

With the terminal pointed at the jest-testing directory, run the test script using npm.

Programming Assignment: Writing a Unit Test Solution

• Copy & paste this code on Files..
• And save your file and then submit.

First Change in this file timesTwo.js

// Task 1: Code the timesTwo function declaration
function timesTwo(num){
    return num * 2;
}

// Task 2: Export the timesTwo function as a module
module.exports = timesTwo;

Second Change in this file timesTwo.test.js

const timesTwo = require('./timesTwo');

// Write the first test
test('returns the number times 2', () => {
    expect(timesTwo(10)).toBe(20);
});