headers-polyfill/src/transformers/listToHeaders.test.ts

A native "Headers" class polyfill.

import { listToHeaders } from './listToHeaders'
import { Headers } from '../Headers'
import { HeadersList } from '../glossary'

describe('given a list representation of headers', () => {
  it('returns a Headers instance', () => {
    const list: HeadersList = [
      ['accept', ['application/json', 'text/plain']],
      ['content-length', '1234'],
      ['content-type', 'application/json'],
    ]

    const headers = listToHeaders(list)
    expect(headers).toBeInstanceOf(Headers)
    expect(headers.get('accept')).toEqual('application/json, text/plain')
    expect(headers.get('content-length')).toEqual('1234')
    expect(headers.get('content-type')).toEqual('application/json')
  })
})