CODEWITHSUNDEEP
javascriptunit-testingtypescriptpromise
Sarawut Positwinyu
Sarawut Positwinyu

Reputation: 5042

Promise won't resolve in unit test

Promise just won't resolve in unit test.

it('should break', function(done){
     const promise =  Promise.resolve([1, 2, 3, 4 , 5]); 
     promise.then(function(){
         expect(true).to.be.false;
         done();
     });
});

I have also tried this. (This is actually works in my seperate new sample project i created but this is not working in my real project so this is weird

import { expect } from 'chai';

describe('Hello function', function () {

it('should return hello world', function () {
    const promise = Promise.resolve(1);
    return promise.then(function () {
        expect(true).to.be.false;
    });
});

});

Background "karma-mocha": "^1.3.0", "karma-webpack": "^2.0.1", "karma-chai": "^0.1.0", "karma-chrome-launcher": "^2.2.0", "typescript": "~2.3.4", "tslint-loader": "^3.3.0",

In karma.config.js

frameworks: ['mocha', 'chai'], browsers: ['ChromeHeadless'],

Error message i got

✖ should break
  HeadlessChrome 0.0.0 (Mac OS X 10.12.6)
Error: Timeout of 9999ms exceeded. For async tests and hooks, ensure "done()" is called; if returning a Promise, ensure it resolves.

Upvotes: 0

Views: 5789

Answers (2)

Evert
Evert

Reputation: 99591

There's 2 ways to do asynchronous tests with mocha. Using done() or by returning a promise.

Because you're using promises, just returning the promise makes the most sense. This example removes done and returns the promise.

it('should break', function(){
  const promise =  Promise.resolve([1, 2, 3, 4 , 5]); 
  return promise.then(function(){
    expect(true).to.be.false();
  });
});

Rewritten as async/await + arrow functions:

it('should break', async () => {
  await [1, 2, 3, 4 , 5];
  expect(true).to.be.false();
});

Using done() is possible but you shouldn't mix returning promises and calling done().

Upvotes: 1

Matt Greenberg
Matt Greenberg

Reputation: 2330

you have to return the promise and call done() after your assertion.

it('should break', function(done){
 const promise =  Promise.resolve([1, 2, 3, 4 , 5]); 
 return promise.then(function(){
     expect(true).to.be.false;
     done();
 });
});

Upvotes: -1

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