Unit testing for NodeJS using the Jest Framework
In this blog, we discuss how to use the Jest Framework for unit testing for NodeJS. Nodejs is an open-source, free, and cross-platform runtime environment for executing JavaScript code outside of the browser, mainly backend. Since it has the most open-source libraries accessible, it is frequently used to create backend services like APIs and is perfect for creating highly scalable, data-intensive, and real-time applications. It is a popular tool for almost any type of application or project.
Unit testing is a level of software testing where individual units/ components or small pieces of software are tested. The purpose is to validate that each block of the software performs. A unit is a small piece of testable part of any software. It usually has a few or one input and usually a single output. In procedural programming, a unit may be an individual program, function, procedure, small piece of application, etc.
It is helpful because it gives users the added benefit of being able to add new features without affecting other aspects of their program.
What is Jest Framework?
Jest is a testing framework developed by Facebook. It was mainly built for React, Node, TypeScript, Angular, Vue, and JavaScript-based applications. Its main priorities are simplicity and support for big web apps. Jasmine was the foundation, and Jest was built upon it.
Features of Jest Framework:
- Zero configuration setup it doesn’t need to do a lot of setup in terms of configuration while working with jest.
- Provides built-in code coverage support.
- Supports snapshot testing.Jest uses BDD-style tests. There is one primary describe block and potential for many test blocks in each test suite. These test blocks are also capable of having nested description blocks.
There are three main methods in the test file:
- describe() – It is a suite of test scripts that provides an overview of the test suite.
- test() – It is the smallest unit test case that is written to be executed.
- expect() – It is an assertion. Every test() statement has an expect() function, which expects a true form return when given a value.
Apart from the above methods, we have more Jest Matchers who assert certain conditions or cases.
Types of Jest Matchers:
Jest statements use matchers to assert a condition. Jest uses matches from the expected API. Let’s go over some of the most popular matchers and Jest tests together.
Equality
This is the most commonly used matcher. This is used for arithmetic operations and for checking equally or not equal.
For Example
test("equality matchers", () => { expect(2*2).toBe(4); expect(4-2).not.toBe(1); })
toBe and not.toBe are analogous is equals and not equals.
Truthiness
This is used for null, falsy, and truthy that is false and true values. Anything that is not logically true is falsy number 0, null, empty, empty string, NaN is all examples of falsy concerning JS.
test("truthy operators", () => { var name="Software testing help" var n = null expect(n).toBeNull() expect(name).not.toBeNull expect(name).toBeTruthy() expect(n).toBeTruthy() expect(n).toBeFalsy() expect(0).toBeFalsy() })
Number Matchers
This is generally used for arithmetic operations like greater than, less than, greater than, or equal, etc.
For Example:
test("numeric operators", () => { var num1 = 100; var num2 = -20; var num3 = 0; expect(num1).toBeGreaterThan(10) expect(num2).toBeLessThanOrEqual(0) expect(num3).toBeGreaterThanOrEqual(0) })
String Matchers
This provides matchers for strings to be matched with a regular expression.
For Example:
test("string matchers",() => { var string1 = "software testing" expect(string1).toMatch(/test/); expect(string1).not.toMatch(/abc/) })