javascript - Possibly not completely understanding exports or jest

Question

Just going over some exercises so I can get more proficient at jest and I'm a little confused about something.

Here is the test subject:

function createRange(start, end) {
    let range = [];

    for (i = start; i <= end; i++) {
        range.push(i);
    }

    return range;
}

function sumRange(start, end) {
    const range = createRange(start, end);
    let sum = 0;

    range.forEach((el) => (sum += el));

    return sum;
}

module.exports = createRange;
module.exports = sumRange;

And this is the test:

const sumRange = require('./sumRange');
const createRange = require('./sumRange');

describe('sumRange()', () => {
    it('sums a given range', () => {
        expect(sumRange(1, 3)).toEqual(6);
    });
});

describe('createRange()', () => {
    it('creates a range between given arguments 1-3', () => {
        expect(createRange(1, 3)).toEqual([1, 2, 3]);
    });

    it('creates a range between given arguments 7-17', () => {
        expect(createRange(7, 11)).toEqual([7, 8, 9, 10, 11]);
    });
});

I first started testing the createRange function and tests were passing. Then moved on to the sumRange function. Once I started testing sumRange the createRange test started failing and were showing the results for sumRange. The results are below:

FAIL ./sumRange.spec.js sumRange() ? sums a given range (4 ms) createRange() ? creates a range between given arguments 1-3 (3 ms) ? creates a range between given arguments 7-17 (1 ms)

● createRange() ? creates a range between given arguments 1-3

expect(received).toEqual(expected) // deep equality

Expected: [1, 2, 3]
Received: 6

  10 | describe('createRange()', () => {
  11 |     it('creates a range between given arguments 1-3', () => {
> 12 |         expect(createRange(1, 3)).toEqual([1, 2, 3]);
     |                                   ^
  13 |     });
  14 | 
  15 |     it('creates a range between given arguments 7-17', () => {

  at Object.it (ch4_DataStructures/sumRange.spec.js:12:35)

● createRange() ? creates a range between given arguments 7-17

expect(received).toEqual(expected) // deep equality

Expected: [7, 8, 9, 10, 11]
Received: 45

  14 | 
  15 |     it('creates a range between given arguments 7-17', () => {
> 16 |         expect(createRange(7, 11)).toEqual([7, 8, 9, 10, 11]);
     |                                    ^
  17 |     });
  18 | });
  19 | 

  at Object.it (ch4_DataStructures/sumRange.spec.js:16:36)

Test Suites: 1 failed, 1 total Tests: 2 failed, 1 passed, 3 total Snapshots: 0 total Time: 0.856 s, estimated 1 s Ran all test suites matching /sumRange.spec.js/i.

Answer 1

The problem is that you are setting module.exports twice, which makes it set to sumRange so you are testing sumRange in both areas. You could do this instead:

module.exports = { createRange, sumRange };

And then import it with:

const { createRange, sumRange } = require("./sumRange");