Testing an Angular service that utilizes $timeout with Jasmine's Mock Clock to ensure accuracy and reliability

Question

Testing an Angular service that utilizes $timeout with Jasmine's Mock Clock to ensure accuracy and reliability

Within one of my angular services, I have a function that needs to be called repeatedly at consistent intervals. My approach involves utilizing $timeout in the following manner:

var interval = 1000; // Or something

var _tick = function () {
     $timeout(function () {
        doStuff();
        _tick();
    }, interval);
};

_tick();

I am currently facing a challenge in unit testing this with Jasmine. How can I achieve this successfully? When using $timeout.flush(), the function calls seem to run endlessly. On the other hand, when employing Jasmine's mock clock, it appears that $timeout remains unaffected. The solution seems within reach if I can make this work:

describe("ANGULAR Manually ticking the Jasmine Mock Clock", function() {
    var timerCallback, $timeout;

    beforeEach(inject(function($injector) {
        $timeout = $injector.get('$timeout');
        timerCallback = jasmine.createSpy('timerCallback');
        jasmine.Clock.useMock();
    }));

    it("causes a timeout to be called synchronously", function() {
        $timeout(function() {
            timerCallback();
        }, 100);
        expect(timerCallback).not.toHaveBeenCalled();
        jasmine.Clock.tick(101);
        expect(timerCallback).toHaveBeenCalled();
    });
});

Although the mentioned approaches are functional, they do not offer the resolution I seek:

describe("Manually ticking the Jasmine Mock Clock", function() {
    var timerCallback;

    beforeEach(function() {
        timerCallback = jasmine.createSpy('timerCallback');
        jasmine.Clock.useMock();
    });

    it("causes a timeout to be called synchronously", function() {
        setTimeout(function() {
            timerCallback();
        }, 100);
        expect(timerCallback).not.toHaveBeenCalled();
        jasmine.Clock.tick(101);
        expect(timerCallback).toHaveBeenCalled();
    });
});

describe("ANGULAR Manually flushing $timeout", function() {
    var timerCallback, $timeout;

    beforeEach(inject(function($injector) {
        $timeout = $injector.get('$timeout');
        timerCallback = jasmine.createSpy('timerCallback');
    }));

    it("causes a timeout to be called synchronously", function() {
        $timeout(function() {
            timerCallback();
        }, 100);
        expect(timerCallback).not.toHaveBeenCalled();
        $timeout.flush();
        expect(timerCallback).toHaveBeenCalled();
    });
});

Your assistance is greatly appreciated!

javascript angularjs jasmine

Answer 1

Answer №1

Avoid turning your test into an Async one by relying on Jasmine's clock. Instead, opt for $timeout.flush() to maintain the flow of the test synchronously. Although setting it up can be a bit challenging at first, once you grasp it, your tests will run faster and with better control.

An illustration of how to implement this method in a test can be found here: https://github.com/angular/angular.js/blob/master/test/ngAnimate/animateSpec.js#L618

Answer 2

Avoid turning your test into an Async one by relying on Jasmine's clock. Instead, opt for $timeout.flush() to maintain the flow of the test synchronously. Although setting it up can be a bit challenging at first, once you grasp it, your tests will run faster and with better control.

An illustration of how to implement this method in a test can be found here: https://github.com/angular/angular.js/blob/master/test/ngAnimate/animateSpec.js#L618

Answer 3

Answer №2

I was inspired by @matsko's answer and decided to share my own solution for the benefit of others looking for a complete approach.

Putting it to the Test

angular.module("app").service("MyService", function() {
    return {
        methodThatHasTimeoutAndReturnsAPromise: function($q, $timeout) {
            var deferred = $q.defer();
            $timeout(function() {
                deferred.resolve(5);
            }, 2000);
            return deferred.promise;
        }
    };
});

The Testing Process

describe("MyService", function() {
    var target,
        $timeout;
    beforeEach(inject(function(_$timeout_, MyService) {
        $timeout = _$timeout_;
        target = MyService;
    }));
    beforeEach(function(done) {
        done();
    });
    it("should return 5", function(done) {
        target.methodThatHasTimeoutAndReturnsAPromise().then(function(value) {
            expect(value).toBe(5);
            done();
        });
        $timeout.flush();
    });
});

Answer 4

I was inspired by @matsko's answer and decided to share my own solution for the benefit of others looking for a complete approach.

Putting it to the Test

angular.module("app").service("MyService", function() {
    return {
        methodThatHasTimeoutAndReturnsAPromise: function($q, $timeout) {
            var deferred = $q.defer();
            $timeout(function() {
                deferred.resolve(5);
            }, 2000);
            return deferred.promise;
        }
    };
});

The Testing Process

describe("MyService", function() {
    var target,
        $timeout;
    beforeEach(inject(function(_$timeout_, MyService) {
        $timeout = _$timeout_;
        target = MyService;
    }));
    beforeEach(function(done) {
        done();
    });
    it("should return 5", function(done) {
        target.methodThatHasTimeoutAndReturnsAPromise().then(function(value) {
            expect(value).toBe(5);
            done();
        });
        $timeout.flush();
    });
});

Testing an Angular service that utilizes $timeout with Jasmine's Mock Clock to ensure accuracy and reliability

Answer №1

Answer №2

Putting it to the Test

The Testing Process

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