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
- 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 |