Wrapper around fetch-mock - a comprehensive, isomorphic mock for the fetch api - which provides an interface that is more idiomatic when working in jest.
The example at the bottom of this readme demonstrates the intuitive API, but shows off only a fraction of fetch-mock's functionality. Features include:
- mocks most of the fetch API spec, even advanced behaviours such as streaming and aborting
- declarative matching for most aspects of a http request, including url, headers, body and query parameters
- shorthands for the most commonly used features, such as matching a http method or matching one fetch only
- support for delaying responses, or using your own async functions to define custom race conditions
- can be used as a spy to observe real network requests
- isomorphic, and supports either a global fetch instance or a locally required instanceg
npm install -D fetch-mock-jest
const fetchMock = require('fetch-mock-jest')
jest.mock('node-fetch', () => require('fetch-mock-jest').sandbox())
const fetchMock = require('node-fetch')
Please refer to the fetch-mock documentation
All jest methods for configuring mock functions are disabled as fetch-mock's own methods should always be used
All the built in jest function inspection assertions can be used, e.g. expect(fetchMock).toHaveBeenCalledWith('http://example.com')
.
fetchMock.mock.calls
and fetchMock.mock.results
are also exposed, giving access to manually inspect the calls.
The following custom jest expectation methods, proxying through to fetch-mock
's inspection methods are also available. They can all be prefixed with the .not
helper for negative assertions.
expect(fetchMock).toHaveFetched(filter, options)
expect(fetchMock).toHaveLastFetched(filter, options)
expect(fetchMock).toHaveNthFetched(n, filter, options)
expect(fetchMock).toHaveFetchedTimes(n, filter, options)
expect(fetchMock).toBeDone(filter)
filter
andoptions
are the same as those used byfetch-mock
's inspection methods- The obove methods can have
Fetched
replaced by any of the following verbs to scope to a particular method: + Got + Posted + Put + Deleted + FetchedHead + Patched
e.g. expect(fetchMock).toHaveLastPatched(filter, options)
fetchMock.mockClear()
can be used to reset the call history
fetchMock.mockReset()
can be used to remove all configured mocks
Please report any bugs in resetting mocks on the issues board
const fetchMock = require('fetch-mock-jest');
const userManager = require('../src/user-manager');
test(async () => {
const users = [{ name: 'bob' }];
fetchMock
.get('http://example.com/users', users)
.post('http://example.com/user', (url, options) => {
if (typeof options.body.name === 'string') {
users.push(options.body);
return 202;
}
return 400;
})
.patch(
{
url: 'http://example.com/user'
},
405
);
expect(await userManager.getAll()).toEqual([{ name: 'bob' }]);
expect(fetchMock).toHaveLastFetched('http://example.com/users
get');
await userManager.create({ name: true });
expect(fetchMock).toHaveLastFetched(
{
url: 'http://example.com/user',
body: { name: true }
},
'post'
);
expect(await userManager.getAll()).toEqual([{ name: 'bob' }]);
fetchMock.mockClear();
await userManager.create({ name: 'sarah' });
expect(fetchMock).toHaveLastFetched(
{
url: 'http://example.com/user',
body: { name: 'sarah' }
},
'post'
);
expect(await userManager.getAll()).toEqual([
{ name: 'bob' },
{ name: 'sarah' }
]);
fetchMock.mockReset();
});