javascript - How to test a method returning a Promise - Stack Overflow

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I'm writing an Angular 2 RC5 application, and unit testing using Karma and Jasmine.

I have a method that returns a Promise<Foo> (It's on top of a call to angular's http.post) I want to run some assertions after that finishes.

Something like this doesn't work

let result = myService.getFoo();
result.then(rslt => expect(1+1).toBe(3)); // the error is lost

This creates an 'Unhandled Promise rejection' warning, but the error is suppressed and the test passes. How do I run assertions based on my resolved promise?

Notes:

• The .catch() method doesn't seem to be what I'm after. I don't want to log or do anything that continues normal program flow, I want to fail the test.
• I've seen code that looks like $rootScope.$digest();. I'm not sure what the typescript equivalent of this sort of thing is. There doesn't seem to be a way of saying: "I have a promise, I'm going to wait here until I have a synchronous result".

I'm writing an Angular 2 RC5 application, and unit testing using Karma and Jasmine.

I have a method that returns a Promise<Foo> (It's on top of a call to angular's http.post) I want to run some assertions after that finishes.

Something like this doesn't work

let result = myService.getFoo();
result.then(rslt => expect(1+1).toBe(3)); // the error is lost

This creates an 'Unhandled Promise rejection' warning, but the error is suppressed and the test passes. How do I run assertions based on my resolved promise?

Notes:

• The .catch() method doesn't seem to be what I'm after. I don't want to log or do anything that continues normal program flow, I want to fail the test.
• I've seen code that looks like $rootScope.$digest();. I'm not sure what the typescript equivalent of this sort of thing is. There doesn't seem to be a way of saying: "I have a promise, I'm going to wait here until I have a synchronous result".

• javascript
• angular
• typescript
• es6-promise

Share Improve this question Follow edited Aug 26, 2016 at 12:37 Estus Flask 223k7878 gold badges472472 silver badges610610 bronze badges asked Aug 26, 2016 at 12:14 NathanNathan 6,53144 gold badges4242 silver badges7979 bronze badges 2

• Do you have babel (specifically babel-polyfill) in your build-stack? You should be able to use async/await to wait for the promise to be fulfilled. – Nik Commented Aug 26, 2016 at 12:19
• Notice that Jasmine allows synchronous specs with jasmine.clock (an alternative to A1's $rootScope.$digest()). – Estus Flask Commented Aug 26, 2016 at 12:37

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2 Answers 2

Sorted by: Reset to default 7

The test should look something like this:

it('should getFoo', function (done) {
  let result = myService.getFoo();
  result
    .then(rslt => expect(rslt).toBe('foo'))
    .then(done);
});

Using the done callback works, but you should be able to do this as well:

(Note the return)

it('should getFoo', function () {
  let result = myService.getFoo();
  return result
    .then(rslt => expect(rslt).toBe('foo'))
});

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