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

A native "Headers" class polyfill.

import { flattenHeadersObject } from './flattenHeadersObject'
import { HeadersObject } from '../glossary'

describe('given a headers object', () => {
  it('flattens its multi-value headers', () => {
    const headersObject: HeadersObject = {
      Accept: ['application/json', 'text/xml'],
      'Content-Type': 'application/pdf',
    }

    expect(flattenHeadersObject(headersObject)).toEqual({
      Accept: 'application/json, text/xml',
      'Content-Type': 'application/pdf',
    })
  })
})