Testing JavaScript callback functions with jasmine - javascript

I have the following functions:
function getPersonData(id) {
retrieveData(
id,
function(person) {
if(person.name) {
displayPerson(person);
}
}
}
function retrieveData(id, successCallBack) {
executeRequest(id, {
success: successCallBack
});
}
getPersonData retrieves a person's information based on the id. It in turn calls retrieveData by passing in the id and a successCallBack function.
retrieveData takes the id and successCallBack and calls another function, executeRequest, which gets the data and passes back a person object.
I am trying to test getPersonData and have the following spec set up
describe("when getPersonData is called with the right person id", function() {
beforeEach(function() {
spyOn(projA.data, "retrieveData").and.returnValue(
{
'name': 'john'
}
);
spyOn(projA.data, "displayPerson");
projA.data.getPersonData("123");
});
it("displays the person's details", function() {
expect(projA.data.displayPerson).toHaveBeenCalled();
);
});
But when the spec is executed the displayPerson method isn't called. This is because the person data being passed back from the success callBack function(person) isn't being passed in even though I have mocked retrieveData to return a result.
My question is:
Is this the right way to test callBack functions? Either way what am I doing wrong?

Ok, so jasmine is tricky in a lot of subtle ways and I think there's two main issues with your code
You have way too many asynchronous calls wrapped in each other. Which is by itself not a problem, but it makes testing in JASMINE hell of a lot harder. For example, what is the point of having a retrieveData function which just calls executeRequest function with the exact same parameters but in a slightly different way.
I rewrote your getPersonData to be like this
function getPersonData(id) {
// this is needed to properly spy in Jasmine
var self = this;
//replaced retrieveData with just execute request
// self is required to properly spy in Jasmine
self.executeRequest(id, {
success: function(person) {
if (person.name) {
self.displayPerson(person);
}
}
})
}
//I don't know what exactly executeRequest does
//but I took the liberty to just make it up for this example
function executeRequest(id, callback) {
callback.success({
name: id
});
}
//I also assumed that projA would look something like this
var projA = {
data: {
getPersonData: getPersonData,
retrieveData: retrieveData,
displayPerson: displayPerson,
executeRequest: executeRequest
}
};
2. In order to test asynchronous code in Jasmine, you need to include a done callback with the test. Also, if you expect a callback function to fire automatically, you need to set it up within a setTimeout function, otherwise it will never fire. Here's an adjusted example:
describe("when getPersonData is called with the right person id", function() {
beforeEach(function() {
//you should not spyOn retriveData or executeCode because it will override the function you wrote and will never call displayPerson
// you should only have spies on the methods you are testing otherwise they will override other methods
spyOn(projA.data, "displayPerson");
});
it("displays the person's details", function(done) {
// it's better to call the function within specific test blocks so you have control over the test
projA.data.getPersonData("123");
// at this point, it will just have called the getPersonData but will not call executeRequest
setTimeout(function() {
//this block will just call executeRequest
setTimeout(function() {
//this block will finally call displayPerson
expect(projA.data.displayPerson).toHaveBeenCalled();
//tell jasmine the test is done after this
done();
})
})
});
})

Related

Meteor js callback not working

I set up a callback function inside my Meteor async method to be called on "readable" event. But the callback is not being called when the on."readable" is being fired (I know it's being fired from the console.log I set up).
Am I missing something here? I've been at it for a few hours now trying a few different things!
Meteor.startup(() => {
Meteor.call("getfeed", function(feedloader) {
//I get: TypeError: undefined is not a function]
console.log(feedloader);
});
});
Meteor.methods({
getfeed: function(callb) {
var req = request('http://feeds.feedburner.com/Techcrunch');
var feedparser = new FeedParser();
testing = [];
//........a bunch of functions........
feedparser.on('readable', function() {
var stream = this
, meta = this.meta
, item;
while (item = stream.read())
{
//I'm pushing the results into testing var
testing.push(item);
}
//From the logs I can see that this is called 12 times
//but the callback's not firing!!!
console.log(testing.length);
callb(testing);
});
}
});
Meteor methods are not asynchronous functions in the sense that they do not get the callback argument even though you pass it when you "call" a method. Instead each method is executed within a Fiber which is another flavor of dealing with asynchronous code.
Fortunately, Meteor has a nice helper that allows you to mix both styles. What you need to do is wrap the "pure" asynchronous part of your method code with Meteor.wrapAsync. This structure should look more or less like this:
Meteor.methods({
getfeed: function() {
var wrapped = Meteor.wrapAsync(function (callb) {
var feedparser = new FeedParser();
testing = [];
// ...
feedparser.on('readable', function() {
// probably the same code you have, but without "callb()"
});
feedparser.on('end', function () {
// NOTE: No error here, so the first argument must be null.
callb(null, testing);
})
});
// NOTE: Finally, call the wrapped function
return wrapped();
}
});

Jasmine testing methods inside .done or .then

Wondering if anyone can help me - I'm trying to test my js using Jasmine (1.3) and I can't figure out the best way to test any method calls inside a .then or a .done method.
example code to explain:
Backbone.View.extend({
myMethod: function () {
this.something.done(function () {
this.doSomethingElse();
}.bind(this));
}
})
I'd like to write a test that check that this.doSomethingElse was called.
I was looking around at jasmine.async and a waitsFor/runs set up but I'm not sure how it fits into external code i.e. I'm not going to call done() inside my actual code to get my test working. Also if I mock out the done method on this.something then I'm not longer testing the actual implementation, right?
I'm just missing how things fit together. If anyone could point me in the right direction I'd really appreciate it!
Update: based on feedback below I've now tried the following
Hey, thanks for the answer - I think maybe I don't have the last part correct - have tried 2 different ways, both initial pass but then fail after a second or 2.
it('calls doSomethingElse on done',function () {
var mockDeferred = $.Deferred();
myView.something = mockDeferred;
spyOn(myView,'doSomethingElse');
mockDeferred.resolve();
waitsFor(function () {
expect(myView.doSomethingElse).toHaveBeenCalled();
});
});
And also:
it('calls doSomethingElse on done',function () {
var mockDeferred = $.Deferred(),
someTrigger = false;
myView.something = mockDeferred;
spyOn(myView,'doSomethingElse');
runs(function () {
mockDeferred.resolve();
someTrigger = true;
});
waitsFor(function () {
someTrigger = true;
});
runs(function () {
expect(myView.doSomethingElse).toHaveBeenCalled();
});
});
In both instances the test will pass originally but then timeout to a failure after a second or 2.
Am I missing something?
To test the example function you described, I would do the following within your test:
Create a new deferred object (I'll call it mockDeferred)
Pass mockDeferred into your code under test so that it is now this.something in your example
Spy on the doSomethingElse function
Call myMethod()
Call resolve() on mockDeferred
Assert that doSomethingElse was called
Edit based on OP's Update:
I don't see anywhere in either of your examples where you are calling myView.myMethod() within your test; make sure you do that. I whipped up an example that you can reference here.
As an aside, I'm surprised the second example you tried passes initially. Maybe because you have some code outside of a runs() block?
Related problem
Spying on a method inside .then and expecting .toHaveBeenCalled fails
Solution:
run test inside fakeAsync and run tick() before the expect
Service:
getFirebaseDoc() {
this.db.firestore.doc('some-doc').get()
.then(this.getFirebaseDocThen)
.catch(this.getFirebaseDocCatch);
}
Unit testing:
it('should call getFirebaseDocThen', fakeAsync(() => { // note `fakeAsync`
spyOn(service, 'getFirebaseDocThen');
spyOn(service.db.firestore, 'doc').and.returnValue({
get: (): any => {
return new Promise((resolve: any, reject: any): any => {
return resolve({ exists: true });
});
},
});
service.getFirebaseDoc();
tick(); // note `tick()`
expect(service.getFirebaseDocThen).toHaveBeenCalled();
}));

Error in testing a Meteor helper function with Jasmine

I have a helper function in MeteorJS as given below:
Template.cars.helpers({
models : function() {
var currentUserId = Meteor.userId();
return cars.find({userId: currentUserId});
}
});
I am trying to write a Jasmine test which will check if the Meteor.userId() function is called once when the models helper is called. I have mocked the Meteor.userId() function,and my code is given below:
describe("test cars collection", function() {
beforeEach(function() {
var Meteor = {
userId: function() {
return 1;
}
};
});
it("userId should be called once", function() {
Template.cars.__helpers[' models']();
spyOn(Meteor, 'userId').and.callThrough();
expect(Meteor.userId.calls.count()).toBe(1);
});
});
However, the result is showing Expected 0 to be 1. I am new to Jasmine and do not really know how to make the correct call to the Meteor.userId() function, while calling the models helper. I think the way I am spying on it is wrong, but I have not been able to figure it out. Can somebody help please?
From the Jasmine Docs
.calls.count(): returns the number of times the spy was called
But you need to set the spy before you call the function, so you can check if your function has been called only once like so:
it("userId should be called once", function() {
spyOn(Meteor, 'userId').and.callThrough(); // <-- spy on the function call first
Template.cars.__helpers[' models'](); // <-- execute the code which calls `Meteor.userId()`
expect(Meteor.userId.calls.count()).toBe(1); // <-- Now this should work
});

sinon spy not wrapping method in asynchronous callback

It appears that sinon.spy(object, method) is not wrapping my object#method as expected.
(I have an uneasy feeling that I'm seeing the same problem as described here and here, but I don't see why this should be. I've instantiated my object before calling sinon.spy(...), and AFAIK I'm not using any cached objects.)
Here's the complete test file:
var
AmbitParser = require('../lib/parsers/ambit-parser'),
expect = require('chai').expect,
sinon = require('sinon');
describe('AmbitParser', function() {
var ambit_parser = new AmbitParser();
describe('#extractLineItems()', function() {
it('calls extractLineItems once', function(done) {
var spy = sinon.spy(ambit_parser, 'extractLineItems');
ambit_parser.parseBills(function gotBills(err, bills) {
expect(ambit_parser.extractLineItems.callCount).to.equal(1); // => expected undefined to equal 1
expect(spy.callCount).to.equal(1); // => expected 0 to equal 1
done();
});
ambit_parser.extractLineItems.restore();
}); // calls extractLineItems once
}); // #extractLineItems
}); // AmbitParser
The call to expect(ambit_parser.extractLineItems.callCount).to.equal(1); results in 'expected undefined to equal 1' and if I change that to expect(spy.callCount).to.equal(1);, I get 'expected 0 to equal 1'.
Together, this makes me think that the call to sinon.spy(...) is not wrapping the ambit_parser.extractLineItems method as expected, but I can't see why this is the case.
The problem is the placement of the call to restore(): it should not be in the body of the test function. Instead, put it in an after() block.
What's happening is that the restore() method is getting called immediately after the test is started, so by the time the callback is executed, the spied upon method has been restored, so sinon will report that the method has never been called.
The following modifications to the original code will work as expected:
describe('AmbitParser', function() {
var ambit_parser = new AmbitParser();
describe('#extractLineItems()', function() {
before(function() {
sinon.spy(ambit_parser, 'extractLineItems');
});
after(function() {
ambit_parser.extractLineItems.restore();
});
it('calls extractLineItems once', function(done) {
ambit_parser.parseBills(function gotBills(err, bills) {
expect(ambit_parser.extractLineItems.callCount).to.equal(1);
done();
});
}); // calls extractLineItems once
}); // #extractLineItems
}); // AmbitParser
Moral of the story: make sure you call reset() only after any callbacks have completed.

jQuery Ajax How do callbacks work?

Hello fellow programmers! I just started an additional programming project and swore to god my code will bo SO much cleaner and easily upgradeable than it has been before.
Then I stumbled upon my "arch enemy" the jQuery AJAX returning. Last time I wanted to return something from an AJAX call I had to bend over and just make the call synchronous. That made things sticky and ugly and I hope that this time I will find something better.
So I have been googling/searching stackoverflow for a while now, and just don't understand this solution many ppl has gotten which is called callback function. Could someone give me an example on how I could exploit these callback functions in order to return my login statuses:
function doLogin(username, password) {
$.ajax({
url: 'jose.php?do=login&user='+username+'&pass='+password,
dataType: 'json',
success: function(data) {
if(data.success==1) {
return('1');
} else {
return('2');
}
$('#spinner').hide();
},
statusCode: {
403:function() {
LogStatus('Slavefile error: Forbidden. Aborting.');
$('#spinner').hide();
return (3);
},
404:function() {
LogStatus('Slavefile was not found. Aborting.');
$('#spinner').hide();
return (3);
},
500:function() {
LogStatus('Slavefile error: Internal server error. Aborting.');
$('#spinner').hide();
return (3);
},
501:function() {
LogStatus('Slavefile error: Not implemented. Aborting.');
$('#spinner').hide();
return (3);
}
},
async: true
});
}
So as you probably know, you cannot use return the way I have done from inside an AJAX call. You should instead use callback functions which I have no idea of how to use.
I'd be VERY greatful if someone could write me this code using callback functions and explaining to me just HOW they WORK.
EDIT:
I REALLY need to return stuff, not use it right away. This function is being called from within another function and should be able to be called from different places without being rewritten even slightly.
/EDIT
Sincerly,
Akke
Web Developer at Oy Aimo Latvala Ab
There are three parts to the basic "I need an asynchronous callback" pattern:
Give the function a callback function parameter.
Call the callback function instead of returning a value.
Instead of calling the function and doing something with its return value, the return value will be passed to your callback function as a parameter.
Suppose your synchronous mind wants to do this:
function doLogin(username, password) {
// ...
return something;
}
switch(doLogin(u, p)) {
case '1':
//...
break;
case '2':
//...
break;
//...
}
but doLogin has to make an asynchronous call to a remote server. You'd just need to rearrange things a little bit like this:
function doLogin(username, password, callback) {
return $.ajax({
// ...
success: function(data) {
if(data.success == 1)
callback('1');
else
callback('2');
},
//...
});
}
var jqxhr = doLogin(u, p, function(statusCode) {
switch(statusCode)) {
case '1':
//...
break;
case '2':
//...
break;
//...
}
});
The jqxhr allows you to reference the AJAX connection before it returns, you'd use it if you needed to cancel the call, attach extra handlers, etc.
A callback is simply a function that runs when certain conditions are met. In this case, it is when ajax has a "success".
You are already using a callback, but you don't recognize it. success: function(data) {} is a callback, but it's just what's called an anonymous function. It has no name or reference, but it still runs. If you want to change this anonymous function to a named function, it is really simple: take the code in the anonymous function, and put it in a named one, and then just call the named one:
[...]success: function(data) {
if(data.success==1) {
return('1');
} else {
return('2');
}
$('#spinner').hide();
}, [...]
should change to:
[...]success: function(){ callbackThingy(data) }, [...]
And now just create the callbackThingy function:
function callbackThingy(data){
if(data.success==1) {
someOtherFunction('1');
} else {
someOtherFunction('2');
}
$('#spinner').hide();
}
Note that the "return" value does nothing. It just stops the callback function, whether you are in an anonymous function or a named one. So you would also have to write a second function called someOtherFunction:
function someOtherFunction(inValue){
if(inValue=='1') {
// do something.
} else if(inValue=='2') {
// do something else.
}
}
The above example is if you have to pass parameters. If you do not need to pass parameters, the setup is simpler:
[...]success: callbackThingy, [...]
function callbackThingy(){
// do something here.
}
From the edit in your original post, I can see that you just need to store a (more) global variable. Try this:
// in the global scope , create this variable:
// (or -- at least -- in the scope available to both this ajax call
// and where you are going to use it)
var valHolder = -1;
// then edit your ajax call like this:
[...]
success: function(data) {
if(data.success==1) {
valHolder = 1;
} else {
valHolder = 2;
}
$('#spinner').hide();
},
[...]
Now you can verify 3 things:
valHolder = -1 means that the ajax call has not yet returned successfully
valHolder = 1 means data.success = 1
valHolder = 2 means data.success != 1.
Another option is to store the variable in an HTML attribute of some element.
Finally, you should probably look at jquery.data for the most jquery way of managing stored data.
Does this help?
Just as a small point of interest, you don't have to include
async : true;
as part of your $.ajax options. The default setting for async is already "true".
Sorry to post this as a response, but until I have 50 rep I can't make a simple comment. (Feel free to help me out with that! ^_^ )

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