How to test function which returns function with parameters?

Catfish Published at Dev

Catfish

I want to test the code below, but i'm unsure how to test this function since it returns a function with parameters. You can see in the image that i'm trying to achieve 100% test coverage and to do that I need a test that gets into the returned function.

const jwt = require('express-jwt')

function validateJwt (tokenConfig) {
  if (!tokenConfig || !tokenConfig.secret) {
    throw new TypeError('tokenConfig param must be defined and have attribute "secret"')
  }

  return (req, res, next) => {
    jwt(_.extend({}, tokenConfig, {
      requestProperty: 'tkn',
      getToken: ReqHelpers.getEitherTkn
    }))
  }
}

Test method which obviously fails with the error AssertionError: expected [Function] to be true

it('should succeed', () => {
  let result = middleware.validateJwt({secret: 'foo'})
  expect(result).to.be.true
})

deerawan

For this kind of test, what we can do is to spy on jwt function call and checking its arguments.

Updated:

since express-jwt return function, we need to involve proxyquire to spy the function. Ref: https://github.com/thlorenz/proxyquire

You can do something like this:

const proxyquire = require('proxyquire');
const sinon = require('sinon');

const jwtSpy = sinon.spy();
const middleware = proxyquire('./middleware', { 'express-jwt': jwtSpy }); // 'express-jwt' comes from your require statement for this package

it('should call jwt', () => {
  const req = sinon.spy();
  const res = sinon.spy();
  const next = sinon.spy();  

  middleware.validateJwt({secret: 'foo'})(req, res, next);

  expect(jwtSpy.called).to.be.ok;
  expect(jwtSpy.calledWithArg({ secret: 'foo', requestProperty: 'tkn'}).to.be.ok; // for checking the arguments
})

Hope it helps

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