Storybook Addon for MSW

An MSW (Mock Service Worker) addon including a control panel that enables interaction and manipulation of mock requests within Storybook.

Features

• Up to date with MSW version (2.2.8)

Installing and Setup

Install MSW and the addon

With npm:

1npm i msw storybook-msw-addon -D

Or with yarn:

1yarn add msw storybook-msw-addon -D

Generate service worker for MSW in a project folder.

Keep in mind this influences the paths you can use for your api calls.

1npx msw init ${path to project folder to be initialized by msw} --save

For example, the following command will init a service worker inside the api folder of your project.

1npx msw init ./api --save

When running Storybook, you have to serve the folder where you have init the MSW service worker as an asset to Storybook. Refer to the docs if needed.

Add the addon to your project

Add the addon to the storybook config in ./storybook/main.js:

1addons: [
2    ...,
3    "storybook-msw-addon",
4  ],

Configure the addon

Enable MSW in Storybook by initializing MSW and providing the MSW loader in ./storybook/preview.js:

Storybook pre-v8.2

1import { initialize, mswLoader } from "storybook-msw-addon";
2
3// Initialize MSW
4initialize();
5
6// Provide the MSW addon loader globally. A loader runs before a story renders, avoiding potential race conditions.
7export const loaders = [mswLoader];

Storybook v8.2+

1import { initialize, mswLoader } from "storybook-msw-addon";
2
3const preview: Preview = {
4  beforeAll: async () => {
5    initialize();
6  },
7  loaders: [mswLoader]
8}

Start Storybook

Remember to serve the public folder, or the path where you have init the MSW service worker

1npm run storybook

Usage

The pass request handlers (https://mswjs.io/docs/basics/request-handler) into the handlers property of the msw parameter. This is commonly an array of handlers.

1import { http, HttpResponse } from "msw";
2
3export const SuccessBehavior = () => <UserProfile />;
4
5SuccessBehavior.parameters = {
6  msw: {
7    handlers: [
8      http.get(endpoint, () => {
9        return HttpResponse.json({ results: results });
10      }),
11    ],
12  },
13};

Advanced Usage

WIP -- Advanced use cases are currently being test with the current version of this addon.

Configuring MSW

If you want to configure storybook-msw--addon, you can pass options to the initialize function.

For example, if you want MSW to bypass unhandled requests you can initialize the addon with the onUnhandledRequest: "bypass" option:

1// preview.js
2import { initialize } from "storybook-msw-addon";
3
4initialize({
5  onUnhandledRequest: "bypass",
6});

Development scripts

• yarn start runs babel in watch mode and starts Storybook
• yarn build build and package your addon code

Acknowledgments

This addon was inspired both by msw-storybook-addon and storybook-addon-mock, motivating us to combine features of both addons in one place.