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fetch-mock

Mock http requests made using fetch

API Documentation

Mocking calls to fetch

mock(matcher, response, options) or mock(options)

Replaces fetch() with a stub which records its calls, grouped by route, and optionally returns a mocked Response object or passes the call through to fetch(). Calls to .mock() can be chained. Note that once mocked, fetch will error on any unmatched calls. Use .spy() or .catch() to handle unmocked calls more gracefully

once()

Shorthand for mock() which limits to being called one time only. (see times option above)

get(), post(), put(), delete(), head(), patch()

Shorthands for mock() restricted to a particular method Tip: if you use some other method a lot you can easily define your own shorthands e.g.:

fetchMock.purge = function (matcher, response, options) {
    return this.mock(matcher, response, Object.assign({}, options, {method: 'PURGE'}));
}

getOnce(), postOnce(), putOnce(), deleteOnce(), headOnce(), patchOnce()

Shorthands for mock() restricted to a particular method and that can only be called one time only

catch(response)

This is used to define how to respond to calls to fetch that don’t match any of the defined mocks. It accepts the same types of response as a normal call to .mock(matcher, response). It can also take an arbitrary function to completely customise behaviour of unmatched calls. It is chainable and can be called before or after other calls to .mock(). If .catch() is called without any parameters then every unmatched call will receive a 200 response e.g.

fetchMock
    .mock('http://my-api.com', 200)
    .catch(503)

spy()

Similar to catch(), this records the call history of unmatched calls, but instead of responding with a stubbed response, the request is passed through to native fetch() and is allowed to communicate over the network.

sandbox(Promise) experimental

This returns a drop-in mock for fetch which can be passed to other mocking libraries. It implements the full fetch-mock api and maintains its own state independent of other instances, so tests can be run in parallel. e.g.

    fetchMock.sandbox().mock('http://domain.com', 200)

sandbox() can optionally be passed a custom promise implementation. If not provided, the Promise global is used.

flush()

Returns a promise that resolves once all fetches handled by fetch-mock have resolved. Useful for testing code that uses fetch but doesn’t return a promise.

restore()

Chainable method that restores fetch() to its unstubbed state and clears all data recorded for its calls.

reset()

Chainable method that clears all data recorded for fetch()’s calls

Note that restore() and reset() are both bound to fetchMock, and can be used directly as callbacks e.g. afterEach(fetchMock.restore) will work just fine. There is no need for afterEach(function () {fetchMock.restore()})

Analysing how fetch() has been called

For the methods below matcherName, if given, should be either the name of a route (see advanced usage below) or equal to matcher.toString() for any unnamed route. You can pass in the original regex or function used as a matcher, but they will be converted to strings and used to look up values in fetch-mock’s internal maps of calls, rather than used as regexes or functions

called(matcherName)

Returns a Boolean indicating whether fetch was called and a route was matched. If matcherName is specified it only returns true if that particular route was matched.

done(matcherName)

Returns a Boolean indicating whether fetch was called the expected number of times (or at least once if the route defines no expectation is set for the route). If no matcherName is passed it returns true if every route has been called the number of expected times.

calls(matcherName)

Returns an object {matched: [], unmatched: []} containing arrays of all calls to fetch, grouped by whether fetch-mock matched them or not. If matcherName is specified then only calls to fetch matching that route are returned.

lastCall(matcherName)

Returns the arguments for the last matched call to fetch

lastUrl(matcherName)

Returns the url for the last matched call to fetch

lastOptions(matcherName)

Returns the options for the last matched call to fetch

Utilities

configure(opts)

Set some global config options, which include

setImplementations(opts)

When using non global fetch (e.g. a ponyfill) or an alternative Promise implementation, this will configure fetch-mock to use your chosen implementations. opts is an object with one or more of the following properties: Headers,Request,Response,Promise. Note that setImplementations(require('fetch-ponyfill')()) will configure fetch-mock to use all of fetch-ponyfill’s classes.