creating and resolving promises in protractor

Question

I am writing a test case for adding store information in the page for Angular app using Protractor, where initially I am counting the number of stores I already have and after the test block is done I expect the count to increase by one so for that I am doing this by following this link of creating promises How to create and manipulate promises in Protractor?

describe('myApp', function() {   var items,startCount;    var testPromise = function(){     items = element.all(by.repeater('store in storelist'));     var deferred = protractor.promise.defer();     items.count().then(function(orgCount){        startCount = orgCount;        console.log('Start Count: '+ startCount); //prints correct value e.g, 6     }, function(error){        console.log(error);     });     return deferred.promise;   };  it('should accept valid data for adding new store', function() {    var cNum = null;    testPromise().then(function(result){       cNum = result;       console.log('cNUm value: '+ cNum); //this value doesn't get printed in console    });    /* Code for adding test fields in store page */     expect(items.count()).toBe(cNum+1);  }); }); 

I expect the store count to be same at the end of the test. count() is resolving a promise and correct value of store count gets printed in testPromise() but in it block when I call testPromise().then method it never goes in that 'then' block

and the end result says

Message:  Expected 6 to be 1.  Stacktrace:   Error: Failed expectation 

I also researched a bit more in webdriver.promise.Promise() from this link http://selenium.googlecode.com/git/docs/api/javascript/class_webdriver_promise_Promise.html and tried using that for creating a promise and resolving its value but not sure what the problem is. Either I get error message saying 'expected 6 to be NaN' or 'expected 6 to be 1' Am I not resolving a promise or writing 'then' block correctly? Would appreciate some insights/help on this issue.

Answer 1

Creation

For creating a promise in protractor, you have to write:

var deferred = protractor.promise.defer(); var promise = deferred.promise; 

---

Callbacks

The callbacks are invoked asynchronously. You can register one (or more) "on success" callbacks:

promise.then(function() {    ... }); 

you can also register one (or more) "on error" callback:

promise.then(null, function() {    ... }); 

These registrations could be chained:

promise.then(function() {    ... }).then(function() {    ... }).then(null, function() {    ... }).then(function() {  }, function() {    ... }).then(onSuccess, onFailure); 

---

Resolution

Success

The "on success" callbacks are invoked when the promise is resolved successfully:

deferred.fulfill(value); 

Failure

The "on failure" callbacks are invoked when the promise is resolved successfully:

deferred.reject(new Error('a problem occurs')); 

---

In your code

you missed the resolution step. You have to fulfill the promise.

A more complete reference is available in the Webdriver.js documentation