单元测试时模拟ES6依赖项

Question

Assume the following two ES6 classes:

my-random.js:

export default class MyRandom {
    get() { return Math.random(); }
}

app.js:

import MyRandom from './random';

export default class App {
    get() {
        let r = new MyRandom();
        let total = r.get() * r.get(); // Complex calc goes here!
        return total;
    }
}

Now I would like to unit test the get from app.js . So I would like to mock MyRandom . Todo this I found a very interesting library Mocktail

According to the docs you should change my-random.js to

import {mock} from 'mocktail';
class MyRandom {
    get() { return Math.random(); }
}
export default mock(MyRandom);

In your test file you have to tell the environment that you're testing as follows:

import {env, ENV, inject} from 'mocktail';
env(ENV.TESTING);

class MyRandomMock {
    get() {
        return 10; // Not so random anymore
    }
}
inject('MyRandom', MyRandomMock);

And you should be able to test app.js . Unfortunately when I try this MyRandom is never replaced with the mock class. Any help would be appreciated!!

I've setup a test project on github here to demonstrate the issue. As you can see the tests will fail :(

If there are better ways to achieve what I need please tell me!

Answer 1

I think you need to import setup before App in your test file, this will inject mock and make it called in App.

import './setup';    
import App from '../src/app';