CODEWITHSUNDEEP
javascriptjasminekarma-runnerkarma-jasminees6-promise
supersan
supersan

Reputation: 6141

Promise .then not triggering when using Karma + Jasmine + PhantomJs?

My unit test is not working hitting the then function for some reason. Here is the test code.

describe("Basic promise test", () => {
    it("should trigger .then function", () => {
        var mock = jasmine.createSpy('some method');
        var promise = new Promise((resolve, reject)=> {
            console.log("inside Promise");
            resolve('something');
            console.log("done!");
        });
        promise.then(mock);         
        promise.then(function () {   //neither works!
            mock();
            console.log("resolved"); //code does reach here but only after test fails
        });

        expect(mock).toHaveBeenCalled();
    });
});

I've tried using 'babel-polyfill', 'es6-promise' and 'promise-polyfill' to no avail. What am I doing wrong?

Jsfiddle for this: https://jsfiddle.net/L53zxe39/

Upvotes: 2

Views: 3188

Answers (1)

Tamas Hegedus
Tamas Hegedus

Reputation: 29906

The promise is resolved, but the then callback is only called in the next microtask, after the check expect(mock).toHaveBeenCalled(); has been made.

It is intended behaviour and designed to prevent ambiguity around promises. A .then callback is guaranteed to be called later, even if the promise is already resolved.

Asynchronous jasmine tests work in the following way:

describe("Basic promise test", () => {
    it("should trigger .then function", (done) => {
        var mock = jasmine.createSpy('some method');
        var promise = new Promise((resolve, reject)=> {
            console.log("inside Promise");
            resolve('something');
            console.log("done!");
        });
        promise.then(mock).then(() => {
          expect(mock).toHaveBeenCalled();
          done();
        }).catch(e => {
          done.fail(e);
        });
    });
});

You can use done.fail to explicitly fail the spec. This is needed to catch and notify jasmine about uncaught exceptions during tests.

Upvotes: 9

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