axios-mock-server

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axios-mock-server

RESTful mock server using axios.

Table of contents

• Features
• Getting Started
  • Installation
  • Tutorial
    • Create API
    • Build API
    • Mocking Axios
  • Examples
• Usage
  • Create an API endpoint
  • Connect to axios
    • Default
    • Each instance
  • Functions
    • setDelayTime(millisecond: number): void
    • enableLog(): void and disableLog(): void
  • TypeScript
  • Cautions
    • .gitignore
    • @ts-ignore, eslint-disable
• Troubleshooting
  • The expected type comes from property 'get' which is declared here on type 'MockMethods' error in TypeScript
• Command Line Interface Options
• Configuration
• License

Features

• You can create a GET/POST/PUT/DELETE API endpoint in a few lines.
• A dedicated server is not required.
• It works with SPA as a static JavaScript file.
• You can use axios as mock-up even in Node.js environment.
• There is an auto-routing function similar to Nuxt.js, and no path description is required.
• Supports TypeScript.

Getting Started

Installation

• Using npm:

  $ npm install axios
  $ npm install axios-mock-server --save-dev
  

• Using Yarn:

  $ yarn add axios
  $ yarn add axios-mock-server --dev
  

Tutorial

Introducing the simplest use of axios-mock-server.

Start the tutorial

Create API

First, create a mocks directory to store the files you want to mock up.

$ mkdir mocks

Next, create an API endpoint file in the mocks directory.
Let's define a mock API that retrieves basic user information with a GET request.

Create a mocks/users directory and create a _userId.js file.

$ mkdir mocks/users
$ touch mocks/users/_userId.js

# If Windows (Command Prompt)
> mkdir mocks\users
> echo. > mocks\users\_userId.js

Add the following to the mocks/users/_userId.js file.

// file: 'mocks/users/_userId.js'
const users = [{ id: 0, name: 'foo' }, { id: 1, name: 'bar' }]

module.exports = {
  get({ values }) {
    return [200, users.find(user => user.id === values.userId)]
  }
}

The routing of axios-mock-server is automatically generated according to the tree structure of JavaScript and TypeScript files in the mocks directory in the same way as the routing of Nuxt.js.

Reference: Routing - Nuxt.js

In other words, the mocks/users/_userId.js file can define an endpoint using dynamic routing as the path of /users/:userId.

Build API

axios-mock-server needs to build and generate the necessary files for routing before running.

$ node_modules/.bin/axios-mock-server

# If Windows (Command Prompt)
> node_modules\.bin\axios-mock-server

If the build is successful, the $mock.js file is generated in themocks directory.

$ cat mocks/\$mock.js
/* eslint-disable */
module.exports = (client) => require('axios-mock-server')([
  {
    path: '/users/_userId',
    methods: require('./users/_userId')
  }
], client)

# If Windows (Command Prompt)
> type mocks\$mock.js

Mocking Axios

Finally, import the mocks/$mock.js file generated by index.js file etc. and pass it to the argument of axios-mock-server.
axios-mock-server will mock up all axios communications by default.

// file: 'index.js'
const axios = require('axios')
const mock = require('./mocks/$mock.js')

mock()

axios.get('https://example.com/users/1').then(({ data }) => {
  console.log(data)
})

If you run the index.js file, you will see that { id: 1, name: 'bar' } is returned.

$ node index.js
{ id: 1, name: 'bar' }

Examples

axios-mock-server can be used to mock up browser usage, data persistence and multipart/form-data format communication.
It is also easy to link with Nuxt.js (@nuxtjs/axios).

See examples for source code.

See a list of use cases

• browser: Use in browser
• node: Use in Node.js (CommonJS)
• with-nuxtjs: Using with a Nuxt.js
• with-typescript: Using with a TypeScript

WIP

• with-in-memory-database

Usage

Create an API endpoint

const users = [{ id: 0, name: 'foo' }, { id: 1, name: 'bar' }]

/**
 * Type definitions for variables passed as arguments in requests
 * @typedef { Object } MockMethodParams
 * @property { import('axios').AxiosRequestConfig } config axios request settings
 * @property {{ [key: string]: string | number }} values Dynamic value of the requested URL (underscore part of the path)
 * @property {{ [key: string]: any }} params The value of the query parameter for the requested URL
 * @property { any } data Request data sent by POST etc.
 */

/**
 * Type definition when response is returned as an object
 * @typedef { Object } MockResponseObject
 * @property { number } status HTTP response status code
 * @property { any? } data Response data
 * @property {{ [key: string]: any }?} headers Response header
 */

/**
 * Response type definition
 * @typedef { [number, any?, { [key: string]: any }?] | MockResponseObject } MockResponse
 */

export default {
  /**
   * All methods such as GET and POST have the same type
   * @param { MockMethodParams }
   * @returns { MockResponse }
   */
  get({ values }) {
    return [200, users.find(user => user.id === values.userId)]
  },

  /**
   * You can also return a response asynchronously
   * @param { MockMethodParams }
   * @returns { Promise<MockResponse> }
   */
  async post({ data }) {
    await new Promise(resolve => setTimeout(resolve, 1000))

    users.push({
      id: users.length,
      name: data.name
    })

    return { status: 201 }
  }
}

Connect to axios

Default

axios-mock-server will mock up all axios communications by default.

import axios from 'axios'
import mock from './mocks/$mock.js'

mock()

axios.get('https://example.com/api/foo').then(response => {
  /* ... */
})

Each instance

You can also mock up each axios instance.

import axios from 'axios'
import mock from './mocks/$mock.js'

const client = axios.create({ baseURL: 'https://example.com/api' })

mock(client)

client.get('/foo').then(response => {
  /* ... */
})

// axios will not be mocked up
axios.get('https://example.com/api/foo').catch(error => {
  console.log(error.response.status) // 404
})

Functions

axios-mock-server has several built-in functions available.

setDelayTime(millisecond: number): void

Simulate response delay.

import axios from 'axios'
import mock from './mocks/$mock.js'

mock().setDelayTime(500)

console.time()
axios.get('https://example.com/api/foo').then(() => {
  console.timeEnd() // default: 506.590ms
})

enableLog(): void and disableLog(): void

Switch request log output.

import axios from 'axios'
import mock from './mocks/$mock.js'

const mockServer = mock()

;(async () => {
  // To enable
  mockServer.enableLog()
  await axios.get('/foo', { baseURL: 'https://example.com/api', params: { bar: 'baz' } }) // stdout -> [mock] get: /foo?bar=baz => 200

  // To disable
  mockServer.disableLog()
  await axios.get('/foo', { baseURL: 'https://example.com/api', params: { bar: 'baz' } }) // stdout ->
})()

TypeScript

axios-mock-server includes TypeScript definitions.

Cautions

.gitignore

Exclude $mock.js or $mock.ts generated by axios-mock-server in the build from Git monitoring.

$ echo "\$mock.*" >> .gitignore

# If Windows (Command Prompt)
> echo $mock.* >> .gitignore

@ts-ignore, eslint-disable

For TypeScript projects, add a // @ ts-ignore comment to the above line that imports$ mock.ts. If @typescript-eslint/ban-ts-ignore rule is enabled in typescript-eslint, please exclude the // @ ts-ignore comment from ESLint.

// eslint-disable-next-line @typescript-eslint/ban-ts-ignore
// @ts-ignore: Cannot find module
import mock from './mocks/$mock'

Troubleshooting

The expected type comes from property 'get' which is declared here on type 'MockMethods' error in TypeScript

When returning a response asynchronously with TypeScript, an error occurs because the type does not match if you try to make the response an array.
Assert MockResponse or return it as an object.

Example of error (Note that the axios-mock-server build will pass!)

import { MockMethods } from 'axios-mock-server'

const methods: MockMethods = {
  async get() {
    await new Promise(resolve => setTimeout(resolve, 100))
    return [200, { foo: 'bar' }] // Error
  }
}

export default methods

Resolve by asserting MockResponse.

import { MockMethods, MockResponse } from 'axios-mock-server'

const methods: MockMethods = {
  async get() {
    await new Promise(resolve => setTimeout(resolve, 100))
    return [200, { foo: 'bar' }] as MockResponse // Type safe
  }
}

export default methods

If the response can be an object, no assertion is required.

import { MockMethods } from 'axios-mock-server'

const methods: MockMethods = {
  async get() {
    await new Promise(resolve => setTimeout(resolve, 100))
    return { status: 200, data: { foo: 'bar' } } // Type safe
  }
}

export default methods

Command Line Interface Options

The following options can be specified in the Command Line Interface.

Option	Type	Default	Description
--config -c	string	".mockserverrc"	Specify the path to the configuration file.
--watch -w			Enable watch mode. Regenerate $mock.js or $mock.ts according to the increase / decrease of the API endpoint file.
--version -v			Print axios-mock-server version.

Configuration

Settings are written in .mockserverrc file with JSON syntax.

Option	Type	Default	Description
input	string | string[]	"mocks" or "apis"	Specify the directory where the API endpoint file is stored. If multiple directories are specified, $mock.js or $mock.ts is generated in each directory.
outputExt	"js" | "ts"		Specify the extension of the file to be generated. The default is set automatically from scripts of the API endpoint file.
outputFilename	string	"$mock.js" or "$mock.ts"	Specify the filename to be generated.
target	"es6" | "cjs"		Specify the code of the module to be generated. The default is set automatically from extension of the API endpoint file.

License

axios-mock-server is licensed under a MIT License.

Changelog

0.19.1 (2021-02-13)

Bug Fixes

• lint and typecheck error (612b1bc)
• deps: [security] bump ini from 1.3.5 to 1.3.7 (e2874d2)
• deps: bump chokidar from 3.4.2 to 3.4.3 (acfe4c4)

Documentation

• update README (1e56cce)