Fake HTTP backend implementation suitable for unit testing applications that use the $http service.
Note: For fake HTTP backend implementation suitable for end-to-end testing or backend-less development please see e2e $httpBackend mock.
During unit testing, we want our unit tests to run quickly and have no external dependencies so we don’t want to send XHR or JSONP requests to a real server. All we really need is to verify whether a certain request has been sent or not, or alternatively just let the application make requests, respond with pre-trained responses and assert that the end result is what we expect it to be.
This mock implementation can be used to respond with static or dynamic responses via the
expect
and when
apis and their shortcuts (expectGET
, whenPOST
, etc).
When an Angular application needs some data from a server, it calls the $http service, which sends the request to a real server using $httpBackend service. With dependency injection, it is easy to inject $httpBackend mock (which has the same API as $httpBackend) and use it to verify the requests and respond with some testing data without sending a request to a real server.
There are two ways to specify what test data should be returned as http responses by the mock backend when the code under test makes http requests:
$httpBackend.expect
- specifies a request expectation$httpBackend.when
- specifies a backend definitionRequest expectations provide a way to make assertions about requests made by the application and to define responses for those requests. The test will fail if the expected requests are not made or they are made in the wrong order.
Backend definitions allow you to define a fake backend for your application which doesn't assert if a particular request was made or not, it just returns a trained response if a request is made. The test will pass whether or not the request gets made during testing.
Request expectations | Backend definitions | |
---|---|---|
Syntax | .expect(...).respond(...) | .when(...).respond(...) |
Typical usage | strict unit tests | loose (black-box) unit testing |
Fulfills multiple requests | NO | YES |
Order of requests matters | YES | NO |
Request required | YES | NO |
Response required | optional (see below) | YES |
In cases where both backend definitions and request expectations are specified during unit testing, the request expectations are evaluated first.
If a request expectation has no response specified, the algorithm will search your backend definitions for an appropriate response.
If a request didn't match any expectation or if the expectation doesn't have the response defined, the backend definitions are evaluated in sequential order to see if any of them match the request. The response from the first matched definition is returned.
The $httpBackend used in production always responds to requests asynchronously. If we preserved
this behavior in unit testing, we'd have to create async unit tests, which are hard to write,
to follow and to maintain. But neither can the testing mock respond synchronously; that would
change the execution of the code under test. For this reason, the mock $httpBackend has a
flush()
method, which allows the test to explicitly flush pending requests. This preserves
the async api of the backend, while allowing the test to execute synchronously.
The following code shows how to setup and use the mock backend when unit testing a controller. First we create the controller under test:
// The module code
angular
.module('MyApp', [])
.controller('MyController', MyController);
// The controller code
function MyController($scope, $http) {
var authToken;
$http.get('/auth.py').then(function(response) {
authToken = response.headers('A-Token');
$scope.user = response.data;
});
$scope.saveMessage = function(message) {
var headers = { 'Authorization': authToken };
$scope.status = 'Saving...';
$http.post('/add-msg.py', message, { headers: headers } ).then(function(response) {
$scope.status = '';
}).catch(function() {
$scope.status = 'Failed...';
});
};
}
Now we setup the mock backend and create the test specs:
// testing controller
describe('MyController', function() {
var $httpBackend, $rootScope, createController, authRequestHandler;
// Set up the module
beforeEach(module('MyApp'));
beforeEach(inject(function($injector) {
// Set up the mock http service responses
$httpBackend = $injector.get('$httpBackend');
// backend definition common for all tests
authRequestHandler = $httpBackend.when('GET', '/auth.py')
.respond({userId: 'userX'}, {'A-Token': 'xxx'});
// Get hold of a scope (i.e. the root scope)
$rootScope = $injector.get('$rootScope');
// The $controller service is used to create instances of controllers
var $controller = $injector.get('$controller');
createController = function() {
return $controller('MyController', {'$scope' : $rootScope });
};
}));
afterEach(function() {
$httpBackend.verifyNoOutstandingExpectation();
$httpBackend.verifyNoOutstandingRequest();
});
it('should fetch authentication token', function() {
$httpBackend.expectGET('/auth.py');
var controller = createController();
$httpBackend.flush();
});
it('should fail authentication', function() {
// Notice how you can change the response even after it was set
authRequestHandler.respond(401, '');
$httpBackend.expectGET('/auth.py');
var controller = createController();
$httpBackend.flush();
expect($rootScope.status).toBe('Failed...');
});
it('should send msg to server', function() {
var controller = createController();
$httpBackend.flush();
// now you don’t care about the authentication, but
// the controller will still send the request and
// $httpBackend will respond without you having to
// specify the expectation and response for this request
$httpBackend.expectPOST('/add-msg.py', 'message content').respond(201, '');
$rootScope.saveMessage('message content');
expect($rootScope.status).toBe('Saving...');
$httpBackend.flush();
expect($rootScope.status).toBe('');
});
it('should send auth header', function() {
var controller = createController();
$httpBackend.flush();
$httpBackend.expectPOST('/add-msg.py', undefined, function(headers) {
// check if the header was sent, if it wasn't the expectation won't
// match the request and the test will fail
return headers['Authorization'] == 'xxx';
}).respond(201, '');
$rootScope.saveMessage('whatever');
$httpBackend.flush();
});
});
You define a response to a request by chaining a call to respond()
onto a definition or expectation.
If you provide a callback as the first parameter to respond(callback)
then you can dynamically generate
a response based on the properties of the request.
The callback
function should be of the form function(method, url, data, headers, params)
.
By default, query parameters on request URLs are parsed into the params
object. So a request URL
of /list?q=searchstr&orderby=-name
would set params
to be {q: 'searchstr', orderby: '-name'}
.
If an expectation or definition uses a regex to match the URL, you can provide an array of keys via a
params
argument. The index of each key in the array will match the index of a group in the
regex.
The params
object in the callback will now have properties with these keys, which hold the value of the
corresponding group in the regex.
This also applies to the when
and expect
shortcut methods.
$httpBackend.expect('GET', /\/user\/(.+)/, undefined, undefined, ['id'])
.respond(function(method, url, data, headers, params) {
// for requested url of '/user/1234' params is {id: '1234'}
});
$httpBackend.whenPATCH(/\/user\/(.+)\/article\/(.+)/, undefined, undefined, ['user', 'article'])
.respond(function(method, url, data, headers, params) {
// for url of '/user/1234/article/567' params is {user: '1234', article: '567'}
});
For extra convenience, whenRoute
and expectRoute
shortcuts are available. These methods offer colon
delimited matching of the url path, ignoring the query string. This allows declarations
similar to how application routes are configured with $routeProvider
. Because these methods convert
the definition url to regex, declaration order is important. Combined with query parameter parsing,
the following is possible:
$httpBackend.whenRoute('GET', '/users/:id')
.respond(function(method, url, data, headers, params) {
return [200, MockUserList[Number(params.id)]];
});
$httpBackend.whenRoute('GET', '/users')
.respond(function(method, url, data, headers, params) {
var userList = angular.copy(MockUserList),
defaultSort = 'lastName',
count, pages, isPrevious, isNext;
// paged api response '/v1/users?page=2'
params.page = Number(params.page) || 1;
// query for last names '/v1/users?q=Archer'
if (params.q) {
userList = $filter('filter')({lastName: params.q});
}
pages = Math.ceil(userList.length / pagingLength);
isPrevious = params.page > 1;
isNext = params.page < pages;
return [200, {
count: userList.length,
previous: isPrevious,
next: isNext,
// sort field -> '/v1/users?sortBy=firstName'
results: $filter('orderBy')(userList, params.sortBy || defaultSort)
.splice((params.page - 1) * pagingLength, pagingLength)
}];
});
when(method, url, [data], [headers], [keys]);
Creates a new backend definition.
Param | Type | Details |
---|---|---|
method | string |
HTTP method. |
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string) |
HTTP request body or function that receives data string and returns true if the data is as expected. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers or function that receives http header object and returns true if the headers match the current definition. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with
|
whenGET(url, [headers], [keys]);
Creates a new backend definition for GET requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
whenHEAD(url, [headers], [keys]);
Creates a new backend definition for HEAD requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
whenDELETE(url, [headers], [keys]);
Creates a new backend definition for DELETE requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
whenPOST(url, [data], [headers], [keys]);
Creates a new backend definition for POST requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string) |
HTTP request body or function that receives data string and returns true if the data is as expected. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
whenPUT(url, [data], [headers], [keys]);
Creates a new backend definition for PUT requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string) |
HTTP request body or function that receives data string and returns true if the data is as expected. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
Creates a new backend definition for JSONP requests. For more info see when()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
Creates a new backend definition that compares only with the requested route.
Param | Type | Details |
---|---|---|
method | string |
HTTP method. |
url | string |
HTTP url string that supports colon param matching. |
requestHandler | Returns an object with |
expect(method, url, [data], [headers], [keys]);
Creates a new request expectation.
Param | Type | Details |
---|---|---|
method | string |
HTTP method. |
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string)Object |
HTTP request body or function that receives data string and returns true if the data is as expected, or Object if request body is in JSON format. |
headers
(optional)
|
Objectfunction(Object) |
HTTP headers or function that receives http header object and returns true if the headers match the current expectation. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with
|
expectGET(url, [headers], [keys]);
Creates a new request expectation for GET requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
expectHEAD(url, [headers], [keys]);
Creates a new request expectation for HEAD requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
expectDELETE(url, [headers], [keys]);
Creates a new request expectation for DELETE requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
expectPOST(url, [data], [headers], [keys]);
Creates a new request expectation for POST requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string)Object |
HTTP request body or function that receives data string and returns true if the data is as expected, or Object if request body is in JSON format. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
expectPUT(url, [data], [headers], [keys]);
Creates a new request expectation for PUT requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string)Object |
HTTP request body or function that receives data string and returns true if the data is as expected, or Object if request body is in JSON format. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
expectPATCH(url, [data], [headers], [keys]);
Creates a new request expectation for PATCH requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives a url and returns true if the url matches the current definition. |
data
(optional)
|
stringRegExpfunction(string)Object |
HTTP request body or function that receives data string and returns true if the data is as expected, or Object if request body is in JSON format. |
headers
(optional)
|
Object |
HTTP headers. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
Creates a new request expectation for JSONP requests. For more info see expect()
.
Param | Type | Details |
---|---|---|
url | stringRegExpfunction(string) |
HTTP url or function that receives an url and returns true if the url matches the current definition. |
keys
(optional)
|
Array |
Array of keys to assign to regex matches in request url described above. |
requestHandler | Returns an object with |
Creates a new request expectation that compares only with the requested route.
Param | Type | Details |
---|---|---|
method | string |
HTTP method. |
url | string |
HTTP url string that supports colon param matching. |
requestHandler | Returns an object with |
Flushes all pending requests using the trained responses.
Param | Type | Details |
---|---|---|
count
(optional)
|
number |
Number of responses to flush (in the order they arrived). If undefined, all pending requests will be flushed. If there are no pending requests when the flush method is called an exception is thrown (as this typically a sign of programming error). |
verifyNoOutstandingExpectation();
Verifies that all of the requests defined via the expect
api were made. If any of the
requests were not made, verifyNoOutstandingExpectation throws an exception.
Typically, you would call this method following each test case that asserts requests using an "afterEach" clause.
afterEach($httpBackend.verifyNoOutstandingExpectation);
Verifies that there are no outstanding requests that need to be flushed.
Typically, you would call this method following each test case that asserts requests using an "afterEach" clause.
afterEach($httpBackend.verifyNoOutstandingRequest);
Resets all request expectations, but preserves all backend definitions. Typically, you would call resetExpectations during a multiple-phase test when you want to reuse the same instance of $httpBackend mock.