What is Jest?
Jest is a popular JavaScript testing framework developed by Facebook. It is widely used for testing React applications but can be used for testing any JavaScript codebase.
Features of Jest:
- Zero configuration – you can get started by just installing Jest and using it. You do not require any extra configuration to start testing your code.
- Mocking – To simulate return values from functions, jest provides a robust framework to mock functions’ return values to suit your test cases.
- Snapshot testing – Creates a copy of the produced HTML file and tests if the current version matches that of the previous snapshot.
- Code coverage – Creates a small interactive website that shows you which lines of code were not tested in your test suite.
- Watch mode – The tests re-run if you make changes to your code.
Syntax:
test('description of the test case', () => {
// Test code goes here
expect(/* actual value */).toBe(/* expected value */);
});
Example: Let’s have a test file that tests the classic “FizzBuzz”
Javascript
const fizzBuzz = require('./index'); describe("Testing FizzBuzz", () => { it("Sending 1 will return '1'", () => { expect(fizzBuzz(1)).toBe("1"); }); it("Sending 2 will return '2'", () => { expect(fizzBuzz(2)).toBe("2"); }); it("Sending 3 will return Fizz", () => { expect(fizzBuzz(3)).toBe("Fizz"); }); it("Sending 4 will return '4'", () => { expect(fizzBuzz(4)).toBe("4"); }); it("Sending 5 will return Buzz", () => { expect(fizzBuzz(5)).toBe("Buzz"); }); it("Sending 6 will return Fizz", () => { expect(fizzBuzz(6)).toBe("Fizz"); }); it("Sending 10 will return Buzz", () => { expect(fizzBuzz(10)).toBe("Buzz"); }); it("Sending 15 will return FizzBuzz", () => { expect(fizzBuzz(15)).toBe("FizzBuzz"); }); it("Sending 30 will return FizzBuzz", () => { expect(fizzBuzz(30)).toBe("FizzBuzz"); }); }); |
Jest vs Mocha: Which one Should You Choose?
When it comes to testing JavaScript applications, selecting the right testing framework can significantly impact your development process and overall project success. Among the available options, Jest and Mocha stand out as two popular choices, each with its own set of features and benefits.
In this article we will see what are Unit tests then we will explore more about Jest and Mocha.
Table of Content
- What are unit tests?
- What is Jest?
- What is Mocha
- Difference between Jest and Mocha.