How to refactor a "callback pyramid" into promise-based version - javascript

I'm currently struggeling to really understand how to refactor my code to use promises/the Q library.
Consider the following common basic example: I have a testcase that imports the same file twice into a mongodb and then checks whether the dataset name for the second import got some modifier at the end.
importDataSet('myFile.csv',function () {
importDataSet('myFile.csv',function () {
DataSet.find({title: 1}, function (err, result) {
result.length.should.be.equal(2);
result[0].title.should.startWith('myFile');
result[1].title.should.startWith('myFile');
result[0].title.should.not.be.equal(result[0].title);
done();
});
});
});
done();
});
(done() is the final callback):
So how would I do this using promises?
Preferably without changing the function signatures, (I followed the convention to have callbacks as the last parameter).

I am not sure why done() is called twice in your code, but without that, it may look similar to:
importDataSet('myFile.csv')
.then(function () {
return importDataSet('myFile.csv')
}).then(function () {
return DataSet.find({title: 1})
}).then(function (result) {
result.length.should.be.equal(2);
result[0].title.should.startWith('myFile');
result[1].title.should.startWith('myFile');
result[0].title.should.not.be.equal(result[0].title);
done();
});

Related

load data from module before test executes

(I asked this question recently and accepted an answer but it's still not what I need.) I really need to create dynamic tests from data loaded from a module. Each item from the array will have it's own describe statement with certain protractor actions. My previous post has an answer that says to use an it statement, but I can't do that because there's too much going on.
My main problem is that the data doesn't get loaded in time for the describe. I had another suggestion to use VCR.js or something similar but I don't think those will work because I'm using a module. Is there a way I can save the data to a separate file and load it in? Would that be a good way to go?
var data = require('get-data'); //custom module here
describe('Test', function() {
var itemsArr;
beforeAll(function(done) {
data.get(function(err, result) {
itemsArr = result; //load data from module
done();
});
})
//error: Cannot read property 'forEach' of undefined
describe('check each item', function() {
itemsArr.forEach(function(item) {
checkItem(item);
});
});
function checkItem (item) {
var itemName = item.name;
describe(itemName, function() {
console.log('describe');
it('should work', function() {
console.log('it');
expect(true).toBeTruthy();
});
});
}
});
UPDATE:
I used Eugene's answer and came up with this. I can't test each individual study how I want because the it statement doesn't fire. Is this problem even solvable??
describe('check each item', function () {
it('should load data', function (done) {
browser.wait(itemsPromise, 5000);
itemsPromise.then(function(itemsArr) {
expect(itemsArr).toBeTruthy();
studyArr = itemsArr.filter(function (item) {
return item.enabled && _.contains(item.tags, 'study');
});
studyCount = studyArr.length;
expect(studies.count()).toEqual(studyCount);
checkItems(studyArr);
done();
});
});
function checkItems (itemsArr) {
itemsArr.forEach(function (item) {
describe(item.id, function () {
console.log('checkItems', item.id);
// doesn't work
it('should work', function (done) {
expect(false).toBeTruthy();
done();
});
});
});
}
});
You're trying to do something that Jasmine does not allow: generating tests after the test suite has started. See this comment on an issue of Jasmine:
Jasmine doesn't support adding specs once the suite has started running. Usually, when I've needed to do this, I've been able to know the list of options ahead of time and just loop through them to make the it calls. [...]
("adding specs" === "adding tests")
The point is that you can generate tests dynamically but only before the test suite has started executing tests. One corollary of this is that the test generation cannot be asynchronous.
Your second attempt does not work because it is trying to add tests to a suite that is already running.
Your first attempt is closer to what you need but it does not work either because describe calls its callback immediately, so beforeAll has not run by the time your describe tries to generate the tests.
Solutions
It all boils down to computing the value of itemsArr before the test suite start executing tests.
You could create a .getSync method that would return results synchronously. Your code would then be something like:
var data = require('get-data'); //custom module here
var itemsArr = data.getSync();
describe('Test', function() {
describe('check each item', function() {
itemsArr.forEach(function(item) {
checkItem(item);
});
});
[...]
If writing .getSync function is not possible, you could have an external process be responsible for producing a JSON output that you could then deserialize into itemsArr. You'd execute this external process with one of the ...Sync functions of child_process.
Here's an example of how the 2nd option could work. I've created a get-data.js file with the following code which uses setTimeout to simulate an asynchronous operation:
var Promise = require("bluebird"); // Bluebird is a promise library.
var get = exports.get = function () {
return new Promise(function (resolve, reject) {
var itemsArr = [
{
name: "one",
param: "2"
},
{
name: "two",
param: "2"
}
];
setTimeout(function () {
resolve(itemsArr);
}, 1000);
});
};
// This is what we run when were are running this module as a "script" instead
// of a "module".
function main() {
get().then(function (itemsArr) {
console.log(JSON.stringify(itemsArr));
});
};
// Check whether we are a script or a module...
if (require.main === module) {
main();
}
Then, inside the spec file:
var child_process = require('child_process');
var itemsArr = JSON.parse(child_process.execFileSync(
"/usr/bin/node", ["get-data.js"]));
describe('Test', function() {
itemsArr.forEach(function(item) {
checkItem(item);
});
function checkItem (item) {
var itemName = item.name;
describe(itemName, function() {
console.log('describe');
it('should work', function() {
console.log('it');
expect(true).toBeTruthy();
});
});
}
});
I've tested the code above using jasmine-node. And the following file structure:
.
├── data.js
├── get-data.js
└── test
└── foo.spec.js
./node_modules has bluebird and jasmine-node in it. This is what I get:
$ ./node_modules/.bin/jasmine-node --verbose test
describe
describe
it
it
Test - 5 ms
one - 4 ms
should work - 4 ms
two - 1 ms
should work - 1 ms
Finished in 0.007 seconds
2 tests, 2 assertions, 0 failures, 0 skipped
Try to use a promise, something like:
var deferred = protractor.promise.defer();
var itemsPromise = deferred.promise;
beforeAll(function() {
data.get(function(err, result) {
deferred.fulfill(result);
});
})
And then:
describe('check each item', function() {
itemsPromise.then(function(itemsArr) {
itemsArr.forEach(function(item) {
checkItem(item);
});
});
});
Another solution I can think of is to use browser.wait to wait until itemsArr becomes not empty.
Is your get-data module doing some browser things with protractor? If so, you will need to set/get itemsArr within the context of the controlFlow. Otherwise it will read all the code in the get-data module, but defer its execution and not wait for it to finish before moving right along to those expect statements.
var data = require('get-data'); //custom module here
var itemsArr;
describe('Test', function() {
beforeAll(function() {
// hook into the controlFlow and set the value of the variable
browser.controlFlow().execute(function() {
data.get(function(err, result) {
itemsArr = result; //load data from module
});
});
});
//error: Cannot read property 'forEach' of undefined
describe('check each item', function() {
// hook into the controlFlow and get the value of the variable (at that point in time)
browser.controlFlow().execute(function() {
itemsArr.forEach(function(item) {
checkItem(item);
});
});
});
function checkItem (item) {
var itemName = item.name;
describe(itemName, function() {
console.log('describe');
it('should work', function() {
console.log('it');
expect(true).toBeTruthy();
});
});
}
});

Run async operations inside gulp job

I'm using gulp-processhtml to update my html based on html comments. I need to pass, using options, same variables to its engine in this way:
gulp.task('buildIndex', ['clean', 'copyStatic'], function () {
return gulp.src('src/static/index.html').pipe(processhtml({
data: { name: 'myname' }
})).pipe(gulp.dest('dist/static'));
});
Everything works fine.
Now I need to retrieve 'myname' value using an async task, for example reading it from filesystem. How can I mix it up this new task inside my gulp stream pipes?
Thanks
I solved in this way using Q and returning a promise:
var deferred = Q.defer();
myAsyncTask(function(myName) {
gulp.src('src/static/index.html').pipe(processhtml({
data: { name: myName }
})).pipe(gulp.dest('dist/static')).on('end', function() {
deferred.resolve();
});
});
return deferred.promise;
Don't know if it's the most elegant way, but it works very well.

How to make multiple http requests in my case

I'm trying to chain a promise with Angular $resource.
I have the following factory:
angular.module('myApp').factory('Product', ['$resource', function ($resource) {
return $resource(
'/api/product/:name',
{ name: '#name' },
{ 'getSub': {
url: '/api/product/getSub/:name',
method: 'GET'}
}
);
}]);
I make multiple queries using my Product factory as such:
Product.query({'name': name}, function(product) {
Product.getSub({'name': product.name}, function(subItem) {
Product.getSub({'name':subItem.name}, function(childItem) {
//do stuff with child item
})
})
})
Is there a better way to do this? I feel like nesting all these calls is not a best practice.
You can chain the promises together!
Product.query({'name': name}).$promise
.then(function(product){
return Product.getSub({'name': product.name}).$promise;
})
.then(function(subItem){
return Product.getSub({'name': subItem.name}).$promise;
})
.then(function(item){
// etc
})
you can use waterfall of async library or implement it yourself.
here's sample code for your case.
async.waterfall([
function(callback) {
Product.query({'name': name}, function(product) {
callback(null, product);
})
},
function(product, callback) {
Product.getSub({'name': product.name}, function(subItem) {
callback(null, product, subItem);
})
},
function(product, subItem, callback) {
Product.getSub({'name':subItem.name}, function(childItem) {
var result = {};
result.childItem = childItem;
result.subItem = subItem;
result.product = product;
callback(null, result);
})
}
], function (err, result) {
//do stuff with result
});
If you want the requests to be done one after another (like you have in your example) you could do a recursive function like this:
in this example i want to upload a couple of images (calling a http route):
$scope.uploadImageLayout = function (currentIndex, numberOfItems) {
if (currentIndex === numberOfItems) {
// in here you could do some last code after everything is done
} else {
Upload.upload({
url: 'localhost:3000/ficheiros',
file: $scope.imagesToUpload[$scope.auxIndex].file
}).success(function (data, status, headers, config) {
if ($scope.auxIndex < numberOfItems) {
$scope.uploadImageLayout(currentIndex + 1, numberOfItems);
}
});
}
};
and the first time you call just do this:
$scope.uploadImageLayout(0, $scope.imagesToUpload.length);
in you case its the same but instead of the Upload.upload request you should have your request and catch the callback function(s).
A useful solution maybe use $q library
https://docs.angularjs.org/api/ng/service/$q
You can use the method $q.all() to send a lot of request and manage only one callback then() or make $q.defer() and resolve por reject your oun promises.
I currently answer this question from a mobile device and i can't make an example. Sorry about that.
If when I get home that mistake trains still try to help

Mobile first - Encrypted Cache Success and Failure Handler

In MobileFirst V6.3 once we call a JSON Store API, Success and failure can be captured using .then() & .fail(). To chain the API calls we can use multiple .then(). Let's say,
WL.JSONStore.startTransaction()
.then(function () {
var data = [{name: 'carlos'}];
return WL.JSONStore.get(collectionName).add(data);
})
.then(function () {
var docs = [{_id: 1, json: {name: 'carlos'}}];
return WL.JSONStore.get(collectionName).remove(docs);
})
.then(function () {
return WL.JSONStore.commitTransaction();
})
.fail(function (errorObject) {
WL.JSONStore.rollbackTransaction()
.then(function () {
// Handle rollback success.
})
.fail(function () {
// Handle rollback failure.
})
});
Since Encrypted Cache API has its own API's callback methods, like below.
WL.EncryptedCache.open(credentials, create_if_none, onCompleteHandler, onErrorHandler);
How to handle Encrypted Cache API chain call's similar to JSON Store[Avoiding callback methods for each API Call's]?
If its not available in out-of-box, is any work around available to achieve the same.
A snippet will be helpful.
The recommendation is to use JSONStore.
Chaining callbacks is not supported out of the box.
The way to do it, is for someone to implement wrappers for the methods that are using callbacks. If you insist on doing that, you'll need to implement something that will look like this:
function wrapper() {
var myVar = $.Deferred();
Wl.EncryptedCache.open(credentials, create_if_none, myVar.resolve, myVar.reject);
return myVar;
}
From the user's code:
wrapper.then(
function() {success flow...},
function() {failure flow...}
);

jasmine: Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL

I have an angular service called requestNotificationChannel:
app.factory("requestNotificationChannel", function($rootScope) {
var _DELETE_MESSAGE_ = "_DELETE_MESSAGE_";
function deleteMessage(id, index) {
$rootScope.$broadcast(_DELETE_MESSAGE_, { id: id, index: index });
};
return {
deleteMessage: deleteMessage
};
});
I am trying to unit test this service using jasmine:
"use strict";
describe("Request Notification Channel", function() {
var requestNotificationChannel, rootScope, scope;
beforeEach(function(_requestNotificationChannel_) {
module("messageAppModule");
inject(function($injector, _requestNotificationChannel_) {
rootScope = $injector.get("$rootScope");
scope = rootScope.$new();
requestNotificationChannel = _requestNotificationChannel_;
})
spyOn(rootScope, '$broadcast');
});
it("should broadcast delete message notification", function(done) {
requestNotificationChannel.deleteMessage(1, 4);
expect(rootScope.$broadcast).toHaveBeenCalledWith("_DELETE_MESSAGE_", { id: 1, index: 4 });
done();
});
});
I read about the Asynchronous Support in Jasmine, but as I am rather new to unit testing with javascript couldn't make it work.
I am receiving an error :
Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL
and my test is taking too long to execute (about 5s).
Can somebody help me providing working example of my code with some explanation?
Having an argument in your it function (done in the code below) will cause Jasmine to attempt an async call.
//this block signature will trigger async behavior.
it("should work", function(done){
//...
});
//this block signature will run synchronously
it("should work", function(){
//...
});
It doesn't make a difference what the done argument is named, its existence is all that matters. I ran into this issue from too much copy/pasta.
The Jasmine Asynchronous Support docs note that argument (named done above) is a callback that can be called to let Jasmine know when an asynchronous function is complete. If you never call it, Jasmine will never know your test is done and will eventually timeout.
Even for async tests, there is a timeout that goes off in this cases, You can work around this error by increasing the value for the limit timeout to evaluate an async Jasmine callback
describe('Helper', function () {
var originalTimeout;
beforeEach(function() {
originalTimeout = jasmine.DEFAULT_TIMEOUT_INTERVAL;
jasmine.DEFAULT_TIMEOUT_INTERVAL = 1000000;
});
afterEach(function() {
jasmine.DEFAULT_TIMEOUT_INTERVAL = originalTimeout;
});
it('Template advance', function(doneFn) {
$.ajax({
url: 'public/your-end-point.mock.json',
dataType: 'json',
success: function (data, response) {
// Here your expected using data
expect(1).toBe(1)
doneFn();
},
error: function (data, response) {
// Here your expected using data
expect(1).toBe(1)
doneFn();
}
});
});
});
Source: http://jasmine.github.io/2.0/introduction.html#section-42
This error can also be caused by leaving out inject when initializing a service/factory or whatever. For example, it can be thrown by doing this:
var service;
beforeEach(function(_TestService_) {
service = _TestService_;
});
To fix it just wrap the function with inject to properly retrieve the service:
var service;
beforeEach(inject(function(_TestService_) {
service = _TestService_;
}));
import { fakeAsync, ComponentFixture, TestBed } from '#angular/core/testing';
use fakeAsync
beforeEach(fakeAsync (() => {
//your code
}));
describe('Intilalize', () => {
it('should have a defined component', fakeAsync(() => {
createComponent();
expect(_AddComponent.ngOnInit).toBeDefined();
}));
});
You can use karma-jasmine plugin to set the default time out interval globally.
Add this config in karma.conf.js
module.exports = function(config) {
config.set({
client: {
jasmine: {
timeoutInterval: 10000
}
}
})
}
This error started out of the blue for me, on a test that had always worked. I couldn't find any suggestions that helped until I noticed my Macbook was running sluggishly. I noticed the CPU was pegged by another process, which I killed. The Jasmine async error disappeared and my tests are fine once again.
Don't ask me why, I don't know. But in my circumstance it seemed to be a lack of system resources at fault.
This is more of an observation than an answer, but it may help others who were as frustrated as I was.
I kept getting this error from two tests in my suite. I thought I had simply broken the tests with the refactoring I was doing, so after backing out changes didn't work, I reverted to earlier code, twice (two revisions back) thinking it'd get rid of the error. Doing so changed nothing. I chased my tail all day yesterday, and part of this morning without resolving the issue.
I got frustrated and checked out the code onto a laptop this morning. Ran the entire test suite (about 180 tests), no errors. So the errors were never in the code or tests. Went back to my dev box and rebooted it to clear anything in memory that might have been causing the issue. No change, same errors on the same two tests. So I deleted the directory from my machine, and checked it back out. Voila! No errors.
No idea what caused it, or how to fix it, but deleting the working directory and checking it back out fixed whatever it was.
Hope this helps someone.
You also get this error when expecting something in the beforeAll function!
describe('...', function () {
beforeAll(function () {
...
expect(element(by.css('[id="title"]')).isDisplayed()).toBe(true);
});
it('should successfully ...', function () {
}
}
Don't use done, just leave the function call empty.
It looks like the test is waiting for some callback that never comes. It's likely because the test is not executed with asynchronous behavior.
First, see if just using fakeAsync in your "it" scenario:
it('should do something', fakeAsync(() => {
You can also use flush() to wait for the microTask queue to finish or tick() to wait a specified amount of time.
In my case, this error was caused by improper use of "fixture.detectChanges()" It seems this method is an event listener (async) which will only respond a callback when changes are detected. If no changes are detected it will not invoke the callback, resulting in a timeout error. Hope this helps :)
Works after removing the scope reference and the function arguments:
"use strict";
describe("Request Notification Channel", function() {
var requestNotificationChannel, rootScope;
beforeEach(function() {
module("messageAppModule");
inject(function($injector, _requestNotificationChannel_) {
rootScope = $injector.get("$rootScope");
requestNotificationChannel = _requestNotificationChannel_;
})
spyOn(rootScope, "$broadcast");
});
it("should broadcast delete message notification with provided params", function() {
requestNotificationChannel.deleteMessage(1, 4);
expect(rootScope.$broadcast).toHaveBeenCalledWith("_DELETE_MESSAGE_", { id: 1, index: 4} );
});
});
What I did was: Added/Updated the following code:
framework: 'jasmine',
jasmineNodeOpts:
{
// Jasmine default timeout
defaultTimeoutInterval: 60000,
expectationResultHandler(passed, assertion)
{
// do something
},
}
As noted by #mastablasta, but also to add that if you call the 'done' argument or rather name it completed you just call the callback completed() in your test when it's done.
// this block signature will trigger async behavior.
it("should work", function(done){
// do stuff and then call done...
done();
});
// this block signature will run synchronously
it("should work", function(){
//...
});
jasmine.DEFAULT_TIMEOUT_INTERVAL = 100000;
Keeping this in the block solved my issue.
it('', () => {
jasmine.DEFAULT_TIMEOUT_INTERVAL = 100000;
});
Instead of
beforeEach(() => {..
use
beforeEach(fakeAsync(() => {..
In my case, a timeout was cause because of a failed injection of a service with providedIn: 'root'. It's not clear why injection failed, nor why there was no early error if there is apparently no instance of provider available.
I was able to work around it by manually providing a value:
TestBed.configureTestingModule({
declarations: [
// ...
],
imports: [
// ...
],
providers: [
// ...
{ provide: MyService, useValue: { /* ... */ } },
]
}).compileComponents();
I have caught the same error because I used the setTimeout function in the component. Example:
ngOnInit(): void {
this.changeState();
}
private changeState(): void {
setTimeout(() => this.state = StateEnum.IN_PROGRESS, 10000);
}
When I changed the timeout from 10000ms to 0 or less than 5000ms (DEFAULT_TIMEOUT_INTERVAL), all tests were passed.
In my case, I was not returning the value from the spy method, hence facing error,
mainMethod(args): Observable<something>{
return nestedMethod().pipe();
}
Your Test should like below,
it('your test case', (done: DoneFn) => {
const testData = {}; // Your data
spyOn(service, 'nestedMethod').and.returnValue(of(testData));
const obxValue = service.mainMethod('your args');
obxValue.pipe(first()).subscribe((data) => {
expect(data).not.toBeUndefined();
done();
});
});
If you have an argument (done) in the it function try to remove it as well it's call within the function itself:
it("should broadcast delete message notification", function(/*done -> YOU SHOULD REMOVE IT */) {
requestNotificationChannel.deleteMessage(1, 4);
expect(rootScope.$broadcast).toHaveBeenCalledWith("_DELETE_MESSAGE_", { id: 1, index: 4 });
// done(); -> YOU SHOULD REMOVE IT
});

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