Jest実行時にReferenceError: fetch is not defined

しらんかった〜。

fetch is not available in Node, which is where Jest is running your tests. Is it an experimental browser technology.

You will need to polyfill the behaviour if you want to make actual http calls, or mock fetch to simulate network requests.

https://github.com/facebook/jest/issues/2071#issuecomment-259709487

yarn add -D whatwg-fetch して

jest.setup.js に

const fetchPolifill = require('whatwg-fetch')

global.fetch = fetchPolifill.fetch
global.Request = fetchPolifill.Request
global.Headers = fetchPolifill.Headers
global.Response = fetchPolifill.Response

• fetch undefined when running tests with jest