Mock http requests made using fetch (or isomorphic-fetch). As well as shorthand methods for the simplest use cases, it offers a flexible API for customising mocking behaviour, and can also be persisted (with resettable state) over a series of tests.
- Browser or nodejs 4 or higher
require('fetch-mock')
- Browser tests when not using a loader that respects the
browser
field of package.json:require('fetch-mock/es5/client')
- Server side tests running in nodejs 0.12 or lower:
require('fetch-mock/es5/server')
You will need to ensure fetch
and Promise
are already available as globals in your environment
To output useful messages for debugging export DEBUG=fetch-mock
require('fetch-mock')
exports a singleton with the following methods
Replaces fetch()
with a stub which records it's calls, grouped by route, and optionally returns a mocked Response
object or passes the call through to fetch()
. Calls to .mock()
can be chained.
matcher
[required]: Condition for selecting which requests to mock Accepts any of the followingstring
: Either an exact url to match e.g. 'http://www.site.com/page.html' or, if the string begins with a^
, the string following the^
must begin the url e.g. '^http://www.site.com' would match 'http://www.site.com' or 'http://www.site.com/page.html'RegExp
: A regular expression to test the url againstFunction(url, opts)
: A function (returning a Boolean) that is passed the url and optsfetch()
is called with.
method
[optional]: only matches requests using this http methodresponse
[required]: Configures the http response returned by the mock. Can take any of the following valuesnumber
: Creates a response with this statusstring
: Creates a 200 response with the string as the response bodyobject
: As long as the object does not contain any of the properties below it is converted into a json string and returned as the body of a 200 response. If any of the properties below are defined it is used to configure aResponse
objectbody
: Set the response body (string
orobject
)status
: Set the response status (defaut200
)headers
: Set the response headers. (object
)throws
: If this property is present then aPromise
rejected with the value ofthrows
is returned
Function(url, opts)
: A function that is passed the url and optsfetch()
is called with and that returns any of the responses listed above
const fetchMock = require('fetch-mock');
fetchMock
.mock('http://domain1', 200)
.mock('http://domain2', 'DELETE', 204);
Restores fetch()
to its unstubbed state and clears all data recorded for its calls
Calls restore()
internally then calls mock()
. This allows you to put some generic calls to mock()
in a beforeEach()
while retaining the flexibility to vary the responses for some tests
Clears all data recorded for fetch()
's calls
Returns an object {matched: [], unmatched: []}
containing arrays of all calls to fetch, grouped by whether fetch-mock matched them or not. If matcher
is specified and is equal to matcher.toString()
for any of the mocked routes then only calls to fetch matching that route are returned.
Returns a Boolean indicating whether fetch was called and a route was matched. If matcher
is specified and is equal to matcher.toString()
for any of the mocked routes then only returns true
if that particular route was matched.
Use a configuration object to define a route to mock.
* name
[optional]: A unique string naming the route. Used to subsequently retrieve references to the calls, grouped by name. If not specified defaults to matcher.toString()
* method
[optional]: http method
* matcher
[required]: as specified above
* response
[required]: as specified above
Pass in an array of route configuration objects
Pas in an object containing more complex config for fine grained control over every aspect of mocking behaviour. May have the following properties
- routes
: Either a single route config object or an array of them (see above)
- responses
: When registerRoute()
(see below) has already been used to register some routes then responses
can be used to override the default response. Its value should be an object mapping route names to responses, which should be similar to those provided in the response
property of stanadard route configurations e.g.
```javascript
responses: {
session: function (url, opts) {
if (opts.headers.authorized) {
return {user: 'dummy-authorized-user'};
} else {
return {user: 'dummy-unauthorized-user'};
}
}
}
```
- `greed`: Determines how the mock handles unmatched requests
- 'none': all unmatched calls get passed through to `fetch()`
- 'bad': all unmatched calls result in a rejected promise
- 'good': all unmatched calls result in a resolved promise with a 200 status
Returns an array of arrays of the arguments passed to fetch()
that matched the given route.
Returns a Boolean denoting whether any calls matched the given route.
Often your application/module will need a mocked response for some http requests in order to initialise properly, even if the content of those calls are not the subject of a given test e.g. a mock response from an authentication service and a multi-variant testing service might be necessary in order to test the UI for a version of a log in form. It's helpful to be able to define some default responses for these services which will exist throughout all or a large subset of your tests. registerRoute()
aims to fulfil this need. All these predefined routes can be overridden when mock(config)
is called.
registerRoute(object)
: An object similar to the route objects accepted bymock()
registerRoute(array)
: An array of the above objectsregisterRoute(name, matcher, response)
: The 3 properties of the route object spread across 3 parameters
Unregisters one or more previously registered routes. Accepts either a string or an array of strings
When using isomorphic-fetch or node-fetch ideally fetch
should be added as a global. If not possible to do so you can still use fetch-mock in combination with mockery in nodejs. To use fetch-mock with with mockery you will need to use this function to prevent fetch-mock trying to mock the function globally.
func
Optional reference tofetch
(or any other function you may want to substitute forfetch
in your tests).
Since fetch-mock v3 calls to mock()
are chainable, so to obtain a reference to the mocked fetch call getMock()
.
var fetch = require('node-fetch');
var fetchMock = require('fetch-mock');
var mockery = require('mockery');
fetchMock.useNonGlobalFetch(fetch);
fetchMock.registerRoute([
...
])
it('should make a request', function (done) {
mockery.registerMock('fetch', fetchMock.mock().getMock());
// test code goes in here
mockery.deregisterMock('fetch');
done();
});
var fetchMock = require('fetch-mock');
// Simplest use case
it('should pretend to be Rambo', done => {
fetchMock.mock('http://rambo.was.ere', 301);
fetch('http://rambo.was.ere')
.then(res => {
expect(fetchMock.calls().length).to.equal(1);
expect(res.status).to.equal(301);
fetchMock.restore();
done();
});
})
// Optionally set up some routes you will always want to mock
// Accepts an array of config objects or three parameters,
// name, matcher and response, to add a single route
fetchMock.registerRoute([
{
name: 'session',
matcher: 'https://sessionservice.host.com',
response: {
body: 'user-12345',
// opts is as expected by https://github.com/bitinn/node-fetch/blob/master/lib/response.js
// headers should be passed as an object literal (fetch-mock will convert it into a Headers instance)
// status defaults to 200
opts: {
headers: {
'x-status': 'unsubscribed'
},
status: 401
}
}
},
{
name: 'geo',
matcher: /^https\:\/\/geoservice\.host\.com/,
// objects will be converted to strings using JSON.stringify before being returned
response: {
body: {
country: 'uk'
}
}
}
])
it('should do A', function () {
fetchMock.mock({
// none: all unmatched calls get sent straight through to the default fetch
// bad: all unmatched calls result in a rejected promise
// good: all unmatched calls result in a resolved promise with a 200 status
greed: 'none'
});
thingToTest.exec();
// returns an array of calls to the session service,
// each item in the array is an array of the arguments passed to fetch
// similar to sinon.spy.args
fetchMock.calls('session') // non empty array
fetchMock.called('geo') // Boolean
// reset all call logs
fetchMock.reset()
fetchMock.calls('session') // undefined
fetchMock.called('geo') // false
// fetch itself is just an ordinary sinon.stub
fetch.calledWith('thing')
// restores fetch and resets all data
fetchMock.restore();
})
describe('content', function () {
before(function () {
// register an additional route, this one has a more complex matching rule
fetchMock.registerRoute('content', function (url, opts) {
return opts.headers.get('x-api-key') && url.test(/^https\:\/\/contentservice\.host\.com/);
}, {body: 'I am an article'});
});
after(function () {
fetchMock.unregisterRoute('content');
})
it('should do B', function () {
fetchMock.mock({
// you can choose to mock a subset of the registered routes
// and even add one to be mocked for this test only
// - the route will exist until fetchMock.restore() is called
routes: ['session', 'content', {
name: 'enhanced-content',
matcher: /^https\:\/\/enhanced-contentservice\.host\.com/,
// responses can be contextual depending on the request
// url and opts parameters are exactly what would be passed to fetch
response: function (url, opts) {
return {body: 'enhanced-article-' + url.split('article-id/')[1]};
}
}]
});
thingToTest.exec();
fetchMock.calls('content') // non empty array
fetchMock.called('enhanced-content') // Boolean
// restores fetch and resets all data
fetchMock.restore();
})
it('should do C', function () {
fetchMock.mock({
// you can override the response for a service for this test only
// this means e.g. you can configure an authentication service to return
// a valid user normally, but only return invalid for the one test
// where you're testing authentication
responses: {
'session': 'invalid-user'
}
});
thingToTest.exec();
// restores fetch and resets all data
fetchMock.restore();
})
});