How to spyOn a service function within the link of a directive? - testing

Question

I have a directive that uses a service function like so:
angular.module('testModule',
['serviceBeingUsed'])
.directive('testDirective', function(serviceBeingUsed) {
return {
restrict: 'AE',
templateUrl: 'testTemplate.tpl.html',
scope: {
boundVar1: "="
},
link: function(scope) {
scope.getRequiredData = function(data){
//gether data using service
serviceBeingUsed.fetchRequiredData(data).then(
function(result){
scope.requiredData = result;
}
);
};
}
};
});
In the above directive I inject the service I wish to use and this service function gets used within the scope function "getRequiredData()" which is inside the "link" of this directive.
I have my test suite set up like so:
describe('test suite', function () {
var scope,
$rootScope,
$compile,
$q,
element,
isoScope,
serviceBeingUsed;
beforeEach(module('testModule'));
beforeEach( inject( function(_$rootScope_,
_$q_,
_$compile_,
_serviceBeingUsed_) {
$rootScope = _$rootScope_;
$compile = _$compile_;
serviceBeingUsed = _serviceBeingUsed_;
$q = _$q_;
//This is where we create the directive and it's options.
element = angular.element('<test-directive bound-var1="blabla"></test-directive>');
//We create a new scope from the rootScope.
scope = $rootScope.$new();
//Now we compile the HTML with the rootscope
$compile(element)(scope);
//digest the changes
scope.$digest();
//We retrieve the isolated scope scope of the directive
isoScope = element.isolateScope();
}));
Now I have a test which runs and passes wherby I can spyOn the isolated scope function "getRequiredData()", this test looks like so:
it('getRequiredData runs', inject(function () {
spyOn(isoScope,"getRequiredData");
isoScope.getRequiredData();
expect(isoScope.getRequiredData).toHaveBeenCalled();
}));
This proves that the link functions CAN be tested however when trying to test if the service function is called the test fails and I have no idea why, the test for the service looks like this:
it('serviceFunction runs', inject(function () {
spyOn(serviceBeingUsed, "serviceFunction").and.callFake(function() {
var deferred = $q.defer();
var data = "returnedDataDummy";
deferred.resolve(data);
return deferred.promise;
});
isoScope.getRequiredData();
expect(serviceBeingUsed.serviceFunction).toHaveBeenCalled();
}));
How can I successfully test if the service function has been called here?

Answer 1

In writing this example I have solved my issue. In my actual code, inside the test "serviceFunction runs" I had also included a spyOn(isoScope,"getRequiredData)"
This has the effect of blocking the inner functionality of the function
getRequiredData()
which meant the the service function inside getRequiredData could never run.
To resolve this issue I needed to edit the spy for the outer function
from:
spyOn(isoScope,"getRequiredData");
to:
spyOn(isoScope,"getRequiredData").and.callThrough();
this simple change means that the function being spied on will also run its inner code and not just register that it has been called.
However one important lesson that I have learned is to not do too much inside each test and to separate the tests as much as possible.
So just to clarify, my original test which failed looked like this:
it('getRequiredData runs', inject(function () {
spyOn(serviceBeingUsed, "serviceFunction").and.callFake(function() {
var deferred = $q.defer();
var data = "returnedDataDummy";
deferred.resolve(data);
return deferred.promise;
});
spyOn(isoScope,"getRequiredData");
isoScope.getRequiredData();
expect(serviceBeingUsed.fetchRequiredData).toHaveBeenCalled();
expect(isoScope.getRequiredData).toHaveBeenCalled();
}));
the fix for this test which passes:
it('getRequiredData runs', inject(function () {
spyOn(serviceBeingUsed, "serviceFunction").and.callFake(function() {
var deferred = $q.defer();
var data = "returnedDataDummy";
deferred.resolve(data);
return deferred.promise;
});
spyOn(isoScope,"getRequiredData").and.callThrough();
isoScope.getRequiredData();
expect(serviceBeingUsed.fetchRequiredData).toHaveBeenCalled();
expect(isoScope.getRequiredData).toHaveBeenCalled();
}));