fetch-mock
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Mock http requests made using fetch (or isomorphic-fetch)
notes
- 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 (see useNonGlobalFetch(func)
below) - fetch-mock doesn't declare
fetch
or Promise
as dependencies; as you're testing fetch
it's assumed you're already taking care of these globals - fetch-mock uses npm debug. To output useful messages for debugging set the environment variable
DEBUG=fetch-mock
- If you prefer documentation by example skip to the bottom of this README
API
require('fetch-mock')
exports a singleton with the following methods
mock(config)
Replaces fetch()
with a sinon stub which, in addition to the default sinon behaviour, records it's calls, grouped by route, and optionally returns a stub response or passes the call through to fetch()
. config
is an optional* object with the following properties.
routes
: Either a single object or an array of similar objects each defining how the mock handles a given request. If multiple routes are specified the first matching route will be used to define the response. Each route object must have the following properties.
name
: A unique string naming the routematcher
: The rule for matching calls to fetch()
. Accepts any of the following
response
: Configures the response object returned by the mock. Can take any of the following values
number
: creates a response with the number as the response statusstring
: creates a 200 response with the string as the response bodyobject
: If the object contains any of the properties body, status, headers, throws; then these properties - all of them optional - are used to construct a response as follows
body
: Returned in the response bodystatus
: Returned in the response statusheaders
: Returned in the response headers. They should be defined as an object literal (property names case-insensitive) which will be converted to a Headers
instancethrows
: If this property is present then a Promise
rejected with the value of throws
is returned
As long as the object does not contain any of the above properties it is converted into a json string and this is returned as the body of a 200 responseFunction(url, opts)
: A function that is passed the url and opts fetch()
is called with and that returns any of the responses listed above
responses
: When registerRoute()
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 listed immediately above e.g.
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
* config
is optional only when preconfigured routes have already been setup
restore()
Restores fetch()
to its unstubbed state and clears all data recorded for its calls
reset()
Clears all data recorded for fetch()
's calls
calls(routeName)
Returns an array of arrays of the arguments passed to fetch()
that matched the given route. '__unmatched' can be passed in to return results for calls not matching any route.
called(routeName)
Returns a Boolean denoting whether any calls matched the given route. '__unmatched' can be passed in to return results for calls not matching any route. If no routeName is passed it returns true
if any fetch calls were made
reMock()
Normally calling mock()
twice without restoring inbetween will throw an error. reMock()
calls restore()
internally before calling mock()
again. This allows you to put a generic call to mock()
in a beforeEach()
while retaining the flexibility to vary the responses for some tests
registerRoute(name, matcher, response)
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()
takes either of the following parameters
object
: An object similar to the route objects accepted by mock()
array
: An array of the above objectsname
, matcher
, response
: The 3 properties of the route object spread across 3 parameters
unregisterRoute(name)
Unregisters one or more previously registered routes. Accepts either a string or an array of strings
useNonGlobalFetch(func)
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 to fetch
(or any other function you may want to substitute for fetch
in your tests). This will be converted to a sinon.stub
and can be accessed via fetchMock.fetch
Mockery example
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());
mockery.deregisterMock('fetch');
done();
});
Example
var fetchMock = require('fetch-mock');
fetchMock.registerRoute([
{
name: 'session',
matcher: 'https://sessionservice.host.com',
response: {
body: 'user-12345',
opts: {
headers: {
'x-status': 'unsubscribed'
},
status: 401
}
}
},
{
name: 'geo',
matcher: /^https\:\/\/geoservice\.host\.com/,
response: {
body: {
country: 'uk'
}
}
}
])
it('should do A', function () {
fetchMock.mock({
greed: 'none'
});
thingToTest.exec();
fetchMock.calls('session')
fetchMock.called('geo')
fetchMock.reset()
fetchMock.calls('session')
fetchMock.called('geo')
fetch.calledWith('thing')
fetchMock.restore();
})
describe('content', function () {
before(function () {
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({
routes: ['session', 'content', {
name: 'enhanced-content',
matcher: /^https\:\/\/enhanced-contentservice\.host\.com/,
response: function (url, opts) {
return {body: 'enhanced-article-' + url.split('article-id/')[1]};
}
}]
});
thingToTest.exec();
fetchMock.calls('content')
fetchMock.called('enhanced-content')
fetchMock.restore();
})
it('should do C', function () {
fetchMock.mock({
responses: {
'session': 'invalid-user'
}
});
thingToTest.exec();
fetchMock.restore();
})
});