jest.md

title	description	created	updated
jest (Javascript Library)	Jest is a javascript library which privides utility functions to write unit tests	2019-11-07	2019-11-07

Jest is a javascript library which privides utility functions to write unit tests. Jest also consists of testrunner which is used to generate a test report by running program in command line.

Installation

1. Using NPM

npm install jest --save--dev

Note: Install jest as dev dependency

Popular jest matcher functions

Equality

Matcher_function	Description
expect(...).toBe();	Check for the equality of data
expect(...).toEqual()	Check for the equality of data

Truthiness

Matcher_function	Description
expect(...).toBeDefined();	To check whether a function returning data or not
expect(...).toBeNull();	Check whether something is null
expect(...).toBeTruthy();	Check whether it returns true
expect(...).toBeFalsy();	Check whether it returns false

Numbers

Matcher_function	Description
expect(...).toBeGreaterThan();	Checks whether number is greater or not
expect(...).toBeGreaterThanOrEqual();	Checks whether number is greater or equal
expect(...).toBeLessThan()	Checks whether number is smaller or not
expect(...).toBeLessThanOrEqual()	Checks whether number is smaller or equal

Strings

Matcher_function	Description
expect(...).toMatch(/regularExp/);

Arrays

Matcher_function	Description
expect(...).toContain();	Checks whether element is present in array or not

Objects

Matcher_function	Description
expect(...).toBe();	Check for the equality of object
expect(...).toEqual()	Check for the equality of object
expect(...).toMatchObject()	Check for the equality of object

Exceptions

Matcher_function	Description
expect(() => { someCode }).toThrow();	Check for the equality of exceptions