Module.exports用于在路径/控制器中进行单元测试

Question

I'm pretty new to NodeJS and unit testing.

I use Jest , but it should be the same "issue" with Mocha or Ava , or whatever ...Because my problem seems to be about export / import ...

I have a file learning.js with some functions

// learning.js

function sum(a, b) {
  return a + b
}

const multiply = (a, b) => a * b

module.exports = { sum: sum, multiply: multiply }

...and a some.test.js file:

// some.test.js

const { sum, multiply } = require('./learning')
// const { sum, multiply } = require('./another')

test('adds 1 + 2 to equal 3', () => {
  expect(sum(1, 2)).toBe(3)
})

test('multiplies 2 x 2 to equal 4', () => {
  expect(multiply(2, 2)).toBe(4)
})

At this point, everything is perfect, my tests run and pass.

However, I've a third file named another.js structured that way (I use express ):

router.get('/another', async function(req, res) {

  // TESTS
  function sum(a, b) {
    return a + b
  }

  const multiply = (a, b) => a * b

  // DO SOME OTHER STUFF...

  res.status(200).send('ok')
})

module.exports = { sum: sum, multiply: multiply }
//module.exports = router

When I try to run the same tests from some.test.js (changing only the require statement to map to another.js ), I can't make it works. My tests fail: TypeError multiply is not a function .

I tried to move export somewhere else, to rename some stuff with dot.notation ... I can't make it work.

Any clue? Thanks!

Answer 1

You're running into a scope problem -- your sum and multiply are out of scope from module.exports , since you're defining them from within your route handler.

Why not try this:

Create a new file helpers.js or services.js -- however you'd describe your functions.

const sum = (a, b) => a + b
const multiply = (a, b) => a * b

module.exports = { sum, multiply }

Then in your express file:

const helpers = require('./helpers.js')

router.get('/another', (req, res) => {
  helpers.sum(1,2)
  helpers.multiply(3,4)
  res.status(200).send('ok')
})

module.exports = router

Then in your test problem, you can require helpers in the same way and test the functions individually.