angularjs - Unit testing a recursive method that calls a promise-returning function -

below simplified version of code trying test: simple queue periodically emptied. each number in queue, http post made send (in example fictional) api address. if post successful, number shifted off queue , next number considered.

class queue {     queue: array<number>;     processingqueue: boolean;      constructor(public $http: angular.ihttpservice) {         this.queue = new array<number>();         this.processingqueue = false;     }      startqueueprocessor() {         this.processingqueue = false;          setinterval(() => {             if (!this.processingqueue)                 this.processqueue();         }, 1000);     }      postnumber(number: number): angular.ihttppromise<{}> {         return this.$http.post('http://mydummyurl.com/givemeanumber', number);     }      processqueue(): void {         this.processingqueue = true; // processing queue, make sure setinterval not trigger processing run          if (this.queue.length !== 0) { // there numbers deal with?             const item = this.queue[0]; // first number in queue              this.postnumber(item) // post (returns promise)                 .then(                 () => { // if successful...                     this.queue.shift(); // we've dealt item, remove queue                     this.processqueue(); // check queue again (recurses until items have been dealt with)                 },                 () => { // if unsuccessful...                     this.processingqueue = false; // went wrong, stop                 }                 );         } else {             this.processingqueue = false; // queue empty, stop processing         }     }      enqueue(number: number): void { // add number queue         this.queue.push(number);     } } 

the test wish create check that, after having 3 items added queue, single call processqueue() empty it.

something (mocked in jasmine):

describe('queueing', () => {     var queueservice;      beforeeach(inject((_$httpbackend_, $injector) => {         httpbackend = _$httpbackend_;         httpbackend.whenpost().respond(200);          queueservice = $injector.get('queue');     }));      it('should clear queue when processqueue() called once', () => {          queueservice.enqueue(1);         queueservice.enqueue(2);         queueservice.enqueue(3);          expect(queueservice.queue.length).tobe(3);          queueservice.processqueue();          // somehow wait processqueue() complete          expect(queueservice.queue.length).tobe(0);     }); }); 

my issue second expect() fails message expected 3 0. assume due promises being returned postnumber() not being waited for, hence queue not empty time second expect() called.

how wait processqueue() complete before attempting assert queue has been emptied?

you should modify processqueue return promise. easiest way marking method async keyword , using await later on:

async processqueue(): promise<void>  {     this.processingqueue = true; // processing queue, make sure setinterval not trigger processing run      if (this.queue.length !== 0)      { // there numbers deal with?         const item = this.queue[0]; // first number in queue          try         {             await this.postnumber(item); // post (returns promise)             // if successful...             this.queue.shift(); // we've dealt item, remove queue             this.processqueue(); // check queue again (recurses until items have been dealt with)         }         catch         {                 this.processingqueue = false; // went wrong, stop         }     }      else      {         this.processingqueue = false; // queue empty, stop processing     } } 

and in test:

it('should clear queue when processqueue() called once', async (done) => {      queueservice.enqueue(1);     queueservice.enqueue(2);     queueservice.enqueue(3);      expect(queueservice.queue.length).tobe(3);      await queueservice.processqueue();      // somehow wait processqueue() complete      expect(queueservice.queue.length).tobe(0);      done(); });     

hope helps.