测试从DOB计算年龄的函数

Question

I have a simple function in Javascript;

  export default function getPupilAge(dob) {
  let a = moment();
  let b = moment(dob);
  return a.diff(b, 'months');
};

I am trying to write tests (I am using AVA).

I would like to write a test that says 'given a date returns 23 months' but the let a = moment(); is always today's date so the returned number of months will change over time.

How do I write this test, or refactor my function to allow testability?

Answer 1

Your function seems to calculate age in months (it uses diff from moment() with 'months' parameter), so you can pass moment().subtract(23, 'month'); that is the current date minus 23 months (see subtract docs). In this case getPupilAge will always be 23 .

Here a live example:

 function getPupilAge(dob) { let a = moment(); let b = moment(dob); return a.diff(b, 'months'); }; let dob = moment().subtract(23, 'month'); console.log(getPupilAge(dob)); 

 <script src="https://cdnjs.cloudflare.com/ajax/libs/moment.js/2.17.1/moment.min.js"></script> 

Answer 2

You can use sinon to fake the date and time.
eg

import test from 'ava';
import sinon from 'sinon';

function getPupilAge(dob) {
  let a = moment(); // here the date will be 2016-12-01T06:00:00.000Z
  let b = moment(dob); //here the date will be what you have specified in dob
  return a.diff(b, 'months');
}

test('fake dates', t => {
    sinon.useFakeTimers(new Date(2016,11,1).getTime());

    const result = getPupilAge("20170620");

    t.is(result,6) //example


});

In your function when you call moment() you will get the fake date.

Answer 3

您可以随时let day = moment("1995-12-25");