Nomnomnom... lets you test your fetch calls.
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README.md

Hungry Fetch

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Nomnomnom … lets you test your fetch calls.

What it doesn’t do

Hungry Fetch does not polyfill the Fetch API. Furthermore it requires Response to be available, so you might actually need to polyfill the Fetch API before using Hungry Fetch.

How does it work?

Hungry Fetch monkey patches window.fetch and saves all calls to fetch(…) with it’s parameters.

Installation

npm install --save-dev hungry-fetch

Examples

Swallow and resolve requests

By default hungryFetch resolves any request with an undefined response.

import hungryFetch from 'hungry-fetch';

test('test network call', () => {
  return fetch('/path/to/nowhere', {
    body: JSON.stringify({
      data: 'I am a body'
    })
  }).then(() => {
    const call = hungryFetch.singleCall();
    expect(call.url).toBe('/path/to/nowhere');
    expect(call.json().data).toBe('I am a body');
  });
});

Mock response

You can mock responses for explicit URLs. You may also use * as url matcher to match any URL. Explicit URLs are stronger weighted than the wildcard matcher, so you can specify a default response and add different responses for explicit URLs.

import hungryFetch from 'hungry-fetch';

test('test response', () => {
  hungryFetch.mockResponse('/path/to/nowhere', {
    data: 'some data'
  });

  return fetch('/path/to/nowhere').then(response => {
    return response.json();
  }).then(body => {
    expect(body.data).toBe('some data');
  });
});

Advanced response

You can set some parameters of the response with the third argument of mockResponse(…).

import hungryFetch from 'hungry-fetch';

test('advanced response', () => {
  hungryFetch.mockResponse('/somewhere', {}, {
    // set custom status code
    status: 204,

    // set custom content type
    contentType: 'plain/text',

    // set additional headers
    headers: {
      'X-MyHeader': 'hello',
    },
  });

  return fetch('/somewhere').then(res => {
    expect(res.status).toBe(204);
    expect(res.headers.get('Content-Type')).toBe('plain/text');
    expect(res.headers.get('X-MyHeader')).toBe('hello');
  });
});